Method and device for measuring features on or near an object

ABSTRACT

A method and device for measuring dimensions of a feature on or near an object using a video inspection device. A reference surface is determined based on reference surface points on the surface of the object. One or more measurement cursors are placed on measurement pixels of an image of the object. Projected reference surface points associated with the measurement pixels on the reference surface are determined. The dimensions of the feature can be determined using the three-dimensional coordinates of at least one of the projected reference surface points.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 62/232,866, entitled METHOD AND SYSTEM FOR MEASURINGFEATURES ON OR NEAR AN OBJECT, filed Sep. 25, 2015, the entirety ofwhich is incorporated by reference herein by reference. This applicationis also a Continuation-in-Part of, and claims priority to, U.S. patentapplication Ser. No. 14/660,464, filed Mar. 17, 2015, and entitledMETHOD AND DEVICE FOR DISPLAYING A TWO-DIMENSIONAL IMAGE OF A VIEWEDOBJECT SIMULTANEOUSLY WITH AN IMAGE DEPICTING THE THREE-DIMENSIONALGEOMETRY OF THE VIEWED OBJECT, the entirety of which is incorporatedherein by reference, and which is a Continuation-in-Part of, and claimspriority to, both (1) U.S. patent application Ser. No. 14/108,976, filedDec. 17, 2013, and entitled METHOD AND DEVICE FOR AUTOMATICALLYIDENTIFYING THE DEEPEST POINT ON THE SURFACE OF AN ANOMALY, the entiretyof which is incorporated herein by reference, and (2) U.S. patentapplication Ser. No. 13/040,678, filed Mar. 4, 2011, and entitled METHODAND DEVICE FOR DISPLAYING A THREE-DIMENSIONAL VIEW OF THE SURFACE OF AVIEWED OBJECT, now U.S. Pat. No. 9,013,469, the entirety of which isincorporated herein by reference.

BACKGROUND

The subject matter disclosed herein relates to a method and device formeasuring dimensions of features on or near an object using a videoinspection device.

Video inspection devices, such as video endoscopes or borescopes, can beused to inspect a surface of an object to identify and analyze anomalies(e.g., pits or dents) on the object that may have resulted from, e.g.,damage, wear, corrosion, or improper installation. In many instances,the surface of the object is inaccessible and cannot be viewed withoutthe use of the video inspection device. For example, a video inspectiondevice can be used to inspect the surface of a blade of a turbine engineon an aircraft or power generation unit to identify any anomalies thatmay have formed on the surface to determine if any repair or furthermaintenance is required. In order to make that assessment, it is oftennecessary to obtain highly accurate dimensional measurements of thesurface and the anomaly to verify that the anomaly does not exceed orfall outside an operational limit or required specification for thatobject.

A video inspection device can be used to obtain and display atwo-dimensional image of the surface of a viewed object showing theanomaly to determine the dimensions of an anomaly on the surface. Thistwo-dimensional image of the surface can be used to generatethree-dimensional data of the surface that provides thethree-dimensional coordinates (e.g., (x, y, z)) of a plurality of pointson the surface, including proximate to an anomaly. In some videoinspection devices, the user can operate the video inspection device ina measurement mode to enter a measurement screen in which the userplaces cursors on the two-dimensional image to determine geometricdimensions of the anomaly.

In many instances, however, the object may be damaged in such a way thatportions of the object may be missing (e.g., a turbine blade or otherobject may have a missing tip) or certain areas on the object are notsufficiently detailed in the image (e.g., along edges of a turbine bladewhere there are small dents caused by foreign object damage or the gapbetween the turbine blade and the shroud). A measurement of the missingportion or insufficiently detailed feature may not be possible sincethree-dimensional coordinates of surface points in the desiredmeasurement area cannot be computed or are of low accuracy (e.g., ifthere are no surface points in the area of a missing portion, if thearea is too dark, too bright, too shiny, or has too much glare orspecular reflections, the area has insufficient detail, the area has toomuch noise, etc.). In other situations, the angle of view of the videoinspection device may be such that the user cannot accurately place acursor on at a desired location on the two-dimensional image to take ameasurement. Furthermore, when viewing the image taken by the videoinspection device, a user may not be able to appreciate the physicalrelationship between the probe and the object to adjust the view ifnecessary.

SUMMARY

A method and device for measuring dimensions of a feature on or near anobject using a video inspection device is disclosed. A reference surfaceis determined based on reference surface points on the surface of theobject. One or more measurement cursors are placed on measurement pixelsof an image of the object. Projected reference surface points associatedwith the measurement pixels on the reference surface are determined. Thedimensions of the feature can be determined using the three-dimensionalcoordinates of at least one of the projected reference surface points.An advantage that may be realized in the practice of some disclosedembodiments is that accurate measurements of object features can betaken even where there is no three-dimensional data or low accuracythree-dimensional data available.

In one embodiment, a method for measuring a feature on or near a viewedobject is disclosed. The method comprises the steps of displaying on amonitor an image of the viewed object, determining the three-dimensionalcoordinates of a plurality of points on a surface of the viewed objectusing a central processor unit, selecting one or more reference surfacepoints from the plurality of points on the surface of the viewed objectusing a pointing device, determining a reference surface using thecentral processor unit, wherein the reference surface is determinedbased on the one or more of the reference surface points, placing one ormore measurement cursors on one or more measurement pixels of the imageusing a pointing device, determining one or more projected referencesurface points associated with the one or more measurement cursors onthe reference surface using the central processor unit, wherein each ofthe one or more projected reference surface points are determined basedon the intersection of a three-dimensional trajectory line from the oneor more measurement pixels and the reference surface, and determiningthe dimensions of the feature on or near the viewed object using thethree-dimensional coordinates of at least one of the one or moreprojected reference surface points using the central processor unit.

The above embodiments are exemplary only. Other embodiments are withinthe scope of the disclosed subject matter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

So that the manner in which the features of the invention can beunderstood, a detailed description of the invention may be had byreference to certain embodiments, some of which are illustrated in theaccompanying drawings. It is to be noted, however, that the drawingsillustrate only certain embodiments of this invention and are thereforenot to be considered limiting of its scope, for the scope of thedisclosed subject matter encompasses other embodiments as well. Thedrawings are not necessarily to scale, emphasis generally being placedupon illustrating the features of certain embodiments of the invention.In the drawings, like numerals are used to indicate like partsthroughout the various views.

FIG. 1 is a block diagram of an exemplary video inspection device;

FIG. 2 is an exemplary image obtained by the video inspection device ofthe object surface of a viewed object having an anomaly in an exemplaryembodiment;

FIG. 3 is a flow diagram of an exemplary method for automaticallyidentifying the deepest point on the surface of an anomaly on a viewedobject shown in the image of FIG. 2 in an exemplary embodiment;

FIG. 4 illustrates an exemplary reference surface determined by thevideo inspection device;

FIG. 5 illustrates an exemplary region of interest determined by thevideo inspection device;

FIG. 6 illustrates another exemplary region of interest determined bythe video inspection device;

FIG. 7 is a graphical representation of an exemplary profile of theobject surface of the viewed object shown in the image of FIG. 1 in anexemplary embodiment;

FIG. 8 is another image obtained by the video inspection device of thesurface of a viewed object having an anomaly in an exemplary embodiment;

FIG. 9 is a flow diagram of a method for displaying three-dimensionaldata for inspection of the surface of the viewed object shown in theimage of FIG. 8 in an exemplary embodiment;

FIG. 10 is a display of a subset of a plurality of surface points in apoint cloud view;

FIG. 11 is a flow diagram of an exemplary method for displaying atwo-dimensional image of viewed object simultaneously with an imagedepicting the three-dimensional geometry of the viewed object in anotherexemplary embodiment;

FIG. 12 is a display of a two-dimensional image and a stereo image ofthe viewed object;

FIG. 13 is a display of a two-dimensional image of the viewed objectwith measurement cursors and a rendered image of the three-dimensionalgeometry of the viewed object in the form of a depth profile image withmeasurement identifiers;

FIG. 14 is a display of a two-dimensional image of the viewed objectwith measurement cursors and a rendered image of the three-dimensionalgeometry of the viewed object in the form of a point cloud view withmeasurement identifiers;

FIG. 15A is another exemplary image obtained by the video inspectiondevice of a turbine blade having a missing corner in an anotherexemplary embodiment;

FIG. 15B is a display of a three-dimensional point cloud view of theturbine blade having a missing corner as shown in FIG. 15A in an anotherexemplary embodiment;

FIG. 15C is another exemplary image obtained by the video inspectiondevice of a turbine blade having a missing corner in an anotherexemplary embodiment;

FIG. 16 illustrates relationship between image pixels, sensor pixels,reference surface coordinates, and object surface coordinates;

FIG. 17 is another exemplary image obtained by the video inspectiondevice of a turbine blade having a missing corner in an anotherexemplary embodiment;

FIG. 18 shows a side by side two-dimensional/three-dimensional view of ameasurement plane and a reference profile;

FIGS. 19A and 19B illustrate techniques for marking an image with avisualization overlay to visualize a defined reference surface, such asa measurement plane;

FIG. 20 shows a point cloud view of an object with field of view linesto provide a visual indication of the orientation of the tip of theprobe of the video inspection device;

FIG. 21 shows a two dimensional image side-by-side with athree-dimensional point cloud view of an object in an exemplaryembodiment;

FIG. 22A shows another two dimensional image side-by-side with a pointcloud view of an object in an exemplary embodiment; and

FIG. 22B shows the geometric relationship between the edge viewing angleof the video inspection device and the reference surface.

DETAILED DESCRIPTION

Embodiments of the disclosed subject matter provide techniques formeasuring dimensions of a feature on or near an object using a videoinspection device. In one embodiment, a reference surface is determinedbased on reference surface points on the surface of the object. One ormore measurement cursors are placed on measurement pixels of an image ofthe object. Projected reference surface points associated with themeasurement pixels on the reference surface are determined. Thedimensions of the feature can be determined using the three-dimensionalcoordinates of at least one of the projected reference surface points.Other embodiments are within the scope of the disclosed subject matter.

FIG. 1 is a block diagram of an exemplary video inspection device 100.It will be understood that the video inspection device 100 shown in FIG.1 is exemplary and that the scope of the invention is not limited to anyparticular video inspection device 100 or any particular configurationof components within a video inspection device 100.

Video inspection device 100 can include an elongated probe 102comprising an insertion tube 110 and a head assembly 120 disposed at thedistal end of the insertion tube 110. Insertion tube 110 can be aflexible, tubular section through which all interconnects between thehead assembly 120 and probe electronics 140 are passed. Head assembly120 can include probe optics 122 for guiding and focusing light from theviewed object 202 onto an imager 124. The probe optics 122 can comprise,e.g., a lens singlet or a lens having multiple components. The imager124 can be a solid state CCD or CMOS image sensor for obtaining an imageof the viewed object 202.

A detachable tip or adaptor 130 can be placed on the distal end of thehead assembly 120. The detachable tip 130 can include tip viewing optics132 (e.g., lenses, windows, or apertures) that work in conjunction withthe probe optics 122 to guide and focus light from the viewed object 202onto an imager 124. The detachable tip 130 can also include illuminationLEDs (not shown) if the source of light for the video inspection device100 emanates from the tip 130 or a light passing element (not shown) forpassing light from the probe 102 to the viewed object 202. The tip 130can also provide the ability for side viewing by including a waveguide(e.g., a prism) to turn the camera view and light output to the side.The tip 130 may also provide stereoscopic optics or structured-lightprojecting elements for use in determining three-dimensional data of theviewed surface. The elements that can be included in the tip 130 canalso be included in the probe 102 itself.

The imager 124 can include a plurality of pixels formed in a pluralityof rows and columns and can generate image signals in the form of analogvoltages representative of light incident on each pixel of the imager124. The image signals can be propagated through imager hybrid 126,which provides electronics for signal buffering and conditioning, to animager harness 112, which provides wires for control and video signalsbetween the imager hybrid 126 and the imager interface electronics 142.The imager interface electronics 142 can include power supplies, atiming generator for generating imager clock signals, an analog frontend for digitizing the imager video output signal, and a digital signalprocessor for processing the digitized imager video data into a moreuseful video format.

The imager interface electronics 142 are part of the probe electronics140, which provide a collection of functions for operating the videoinspection device 10. The probe electronics 140 can also include acalibration memory 144, which stores the calibration data for the probe102 and/or tip 130. A microcontroller 146 can also be included in theprobe electronics 140 for communicating with the imager interfaceelectronics 142 to determine and set gain and exposure settings, storingand reading calibration data from the calibration memory 144,controlling the light delivered to the viewed object 202, andcommunicating with a central processor unit (CPU) 150 of the videoinspection device 100.

In addition to communicating with the microcontroller 146, the imagerinterface electronics 142 can also communicate with one or more videoprocessors 160. The video processor 160 can receive a video signal fromthe imager interface electronics 142 and output signals to variousmonitors 170, 172, including an integral display 170 or an externalmonitor 172. The integral display 170 can be an LCD screen built intothe video inspection device 100 for displaying various images or data(e.g., the image of the viewed object 202, menus, cursors, measurementresults) to an inspector. The external monitor 172 can be a videomonitor or computer-type monitor connected to the video inspectiondevice 100 for displaying various images or data.

The video processor 160 can provide/receive commands, statusinformation, streaming video, still video images, and graphical overlaysto/from the CPU 150 and may be comprised of FPGAs, DSPs, or otherprocessing elements which provide functions such as image capture, imageenhancement, graphical overlay merging, distortion correction, frameaveraging, scaling, digital zooming, overlaying, merging, flipping,motion detection, and video format conversion and compression.

The CPU 150 can be used to manage the user interface by receiving inputvia a joystick 180, buttons 182, keypad 184, and/or microphone 186, inaddition to providing a host of other functions, including image, video,and audio storage and recall functions, system control, and measurementprocessing. The joystick 180 can be manipulated by the user to performsuch operations as menu selection, cursor movement, slider adjustment,and articulation control of the probe 102, and may include a push-buttonfunction. The buttons 182 and/or keypad 184 also can be used for menuselection and providing user commands to the CPU 150 (e.g., freezing orsaving a still image). The microphone 186 can be used by the inspectorto provide voice instructions to freeze or save a still image.

The video processor 160 can also communicate with video memory 162,which is used by the video processor 160 for frame buffering andtemporary holding of data during processing. The CPU 150 can alsocommunicate with CPU program memory 152 for storage of programs executedby the CPU 150. In addition, the CPU 150 can be in communication withvolatile memory 154 (e.g., RAM), and non-volatile memory 156 (e.g.,flash memory device, a hard drive, a DVD, or an EPROM memory device).The non-volatile memory 156 is the primary storage for streaming videoand still images.

The CPU 150 can also be in communication with a computer I/O interface158, which provides various interfaces to peripheral devices andnetworks, such as USB, Firewire, Ethernet, audio I/O, and wirelesstransceivers. This computer I/O interface 158 can be used to save,recall, transmit, and/or receive still images, streaming video, oraudio. For example, a USB “thumb drive” or CompactFlash memory card canbe plugged into computer I/O interface 158. In addition, the videoinspection device 100 can be configured to send frames of image data orstreaming video data to an external computer or server. The videoinspection device 100 can incorporate a TCP/IP communication protocolsuite and can be incorporated in a wide area network including aplurality of local and remote computers, each of the computers alsoincorporating a TCP/IP communication protocol suite. With incorporationof TCP/IP protocol suite, the video inspection device 100 incorporatesseveral transport layer protocols including TCP and UDP and severaldifferent layer protocols including HTTP and FTP.

It will be understood that, while certain components have been shown asa single component (e.g., CPU 150) in FIG. 1, multiple separatecomponents can be used to perform the functions of the CPU 150.

FIG. 2 is an exemplary image 200 obtained by the video inspection device100 of the object surface 210 of a viewed object 202 having an anomaly204 in an exemplary embodiment of the invention. In this example, theanomaly 204 is shown as a dent, where material has been removed from theobject surface 210 of the viewed object 202 in the anomaly 204 by damageor wear. It will be understood that the anomaly 204 shown in thisexemplary embodiment is just an example and that the inventive methodapplies to other types of irregularities (e.g., cracks, corrosionpitting, coating loss, surface deposits, etc.). Once the image 200 isobtained, and the anomaly 204 is identified, the image 200 can be usedto determine the dimensions of the anomaly 204 (e.g., height or depth,length, width, area, volume, point to line, profile slice, etc.). In oneembodiment, the image 200 used can be a two-dimensional image 200 of theobject surface 210 of the viewed object 202, including the anomaly 204.

FIG. 3 is a flow diagram of an exemplary method 300 for automaticallyidentifying the deepest point on the object surface 210 of an anomaly204 on a viewed object 202 shown in the image 200 of FIG. 2 in anexemplary embodiment of the invention. It will be understood that thesteps described in the flow diagram of FIG. 3 can be performed in adifferent order than shown in the flow diagram and that not all of thesteps are required for certain embodiments.

At step 310 of the exemplary method 300 (FIG. 3) and as shown in FIG. 2,the user can use the video inspection device 100 (e.g., the imager 124)to obtain at least one image 200 of the object surface 210 of a viewedobject 202 having an anomaly 204 and display it on a video monitor(e.g., an integral display 170 or external monitor 172). In oneembodiment, the image 200 can be displayed in a measurement mode of thevideo inspection device.

At step 320 of the exemplary method 300 (FIG. 3), the video inspectiondevice 100 (e.g., the CPU 150) can determine the three-dimensionalcoordinates (e.g., (x, y, z)) of a plurality of surface points on theobject surface 210 of the viewed object 202, including surface points ofthe anomaly 204. In one embodiment, the video inspection device cangenerate three-dimensional data from the image 200 in order to determinethe three-dimensional coordinates. Several different existing techniquescan be used to provide the three-dimensional coordinates of the surfacepoints in the image 200 (FIG. 2) of the object surface 210 (e.g.,stereo, scanning systems, stereo triangulation, structured light methodssuch as phase shift analysis, phase shift moiré, laser dot projection,etc.).

Most such techniques comprise the use of calibration data, which, amongother things, includes optical characteristic data that is used toreduce errors in the three-dimensional coordinates that would otherwisebe induced by optical distortions. With some techniques, thethree-dimensional coordinates may be determined using one or more imagescaptured in close time proximity that may include projected patterns andthe like. It is to be understood that references to three-dimensionalcoordinates determined using image 200 may also comprisethree-dimensional coordinates determined using one or a plurality ofimages 200 of the object surface 210 captured in close time proximity,and that the image 200 displayed to the user during the describedoperations may or may not actually be used in the determination of thethree-dimensional coordinates.

At step 330 of the exemplary method 300 (FIG. 3), and as shown in FIG.4, the video inspection device 100 (e.g., the CPU 150) can determine areference surface 250. In some embodiments, the reference surface 250can be flat, while in other embodiments the reference surface 250 can becurved. Similarly, in one embodiment, the reference surface 250 can bein the form of a plane, while in other embodiments, the referencesurface 250 can be in the form of a different shape (e.g., cylinder,sphere, etc.). For example, a user can use the joystick 180 (or otherpointing device (e.g., mouse, touch screen)) of the video inspectiondevice 100 to select one or more reference surface points on the objectsurface 210 of the viewed object 202 proximate to the anomaly 204 todetermine a reference surface.

In one embodiment and as shown in FIG. 4, a total of three referencesurface points 221, 222, 223 are selected on the object surface 210 ofthe viewed object 202 proximate to the anomaly 204 to conduct a depthmeasurement of the anomaly 204, with the three reference surface points221, 222, 223 selected on the object surface 210 proximate to theanomaly 204. In one embodiment, the plurality of reference surfacepoints 221, 222, 223 on the object surface 210 of the viewed object 202can be selected by placing reference surface cursors 231, 232, 233 (orother pointing devices) on pixels 241, 242, 243 of the image 200corresponding to the plurality of reference surface points 221, 222, 223on the object surface 210. In the exemplary depth measurement, the videoinspection device 100 (e.g., the CPU 150) can determine thethree-dimensional coordinates of each of the plurality of referencesurface points 221, 222, 223.

The three-dimensional coordinates of three or more surface pointsproximate to one or more of the three reference surface points 221, 222,223 selected on the object surface 210 proximate to the anomaly 204 canbe used to determine a reference surface 250 (e.g., a plane). In oneembodiment, the video inspection device 100 (e.g., the CPU 150) canperform a curve fitting of the three-dimensional coordinates of thethree reference surface points 221, 222, 223 to determine an equationfor the reference surface 250 (e.g., for a plane) having the followingform:k _(0RS) +k _(1RS1) ·x _(iRS) +k _(2RS) ·y _(iRS1) =z _(iRS)  (1)where (x_(iRS), y_(iRS), z_(iRS)) are coordinates of anythree-dimensional point on the defined reference surface 250 andk_(0RS), k_(1RS), and k_(2RS) are coefficients obtained by a curvefitting of the three-dimensional coordinates.

It should be noted that a plurality of reference surface points (i.e.,at least as many points as the number of k coefficients) are used toperform the curve fitting. The curve fitting finds the k coefficientsthat give the best fit to the points used (e.g., least squaresapproach). The k coefficients then define the plane or other referencesurface 250 that approximates the three-dimensional points used.However, if more points are used in the curve fitting than the number ofk coefficients, when you insert the x and y coordinates of the pointsused into the plane equation (1), the z results will generally notexactly match the z coordinates of the points due to noise and anydeviation from a plane that may actually exist. Thus, the x_(iRS1) andy_(iRS1) can be any arbitrary values, and the resulting z_(iRS) tellsyou the z of the defined plane at x_(iRS), y_(iRS). Accordingly,coordinates shown in these equations can be for arbitrary points exactlyon the defined surface, not necessarily the points used in the fittingto determine the k coefficients.

In other embodiments, there are only one or two reference surface pointsselected, prohibiting the use of curve fitting based only on thethree-dimensional coordinates of those reference surface points sincethree points are needed to determine k_(0RS), k_(1RS), and k_(2RS). Inthat case, the video inspection device 100 (e.g., the CPU 150) canidentify a plurality of pixels proximate to each of the pixels of theimage corresponding to a plurality of points on the object surface 210proximate to the reference surface point(s), and determine thethree-dimensional coordinates of the proximate point(s), enabling curvefitting to determine a reference surface 250.

While the exemplary reference surface 250 has been described as beingdetermined based on reference surface points 221, 222, 223 selected byreference surface cursors 231, 232, 233, in other embodiments, thereference surface 250 can be formed by using a pointing device to placea reference surface shape 260 (e.g., circle, square, rectangle,triangle, etc.) proximate to anomaly 204 and using the reference surfacepoints 261, 262, 263, 264 of the shape 260 to determine the referencesurface 250. It will be understood that the reference surface points261, 262, 263, 264 of the shape 260 can be points selected by thepointing device or be other points on or proximate to the perimeter ofthe shape that can be sized to enclose the anomaly 204.

At step 340 of the exemplary method 300 (FIG. 3), and as shown in FIG.5, the video inspection device 100 (e.g., the CPU 150) determines aregion of interest 270 proximate to the anomaly 204 based on thereference surface points of the reference surface 250. The region ofinterest 270 includes a plurality of surface points of the anomaly 204.In one embodiment, a region of interest 270 is formed by forming aregion of interest shape 271 (e.g., a circle) based on two or more ofthe reference surface points 221, 222, 223. In another embodiment, theregion of interest 270 can be determined by forming a cylinderperpendicular to the reference surface 260 and passing it through orproximate to two or more of the reference surface points 221, 222, 223.Referring again to FIG. 4, a region of interest could be formed withinthe reference surface shape 260 and reference surface points 261, 262,263, 264.

Although the exemplary region of interest shape 271 in FIG. 5 is formedby passing through the reference surface points 221, 222, 223, inanother embodiment, a smaller diameter reference surface shape can beformed by passing only proximate to the reference surface points. Forexample, as shown in FIG. 6, a region of interest 280 is formed bypassing a region of interest shape 281 (e.g., a circle) proximate to twoof the reference surface points 221, 222, where the diameter of thecircle 281 is smaller than the distance between the two referencesurface points 221, 222. It will be understood that region of interestshapes 271, 281 and the regions of interest 270, 280 may or may not bedisplayed on the image 200.

After the region of interest 270, 280 is determined, at step 350 of theexemplary method 300 (FIG. 3), the video inspection device 100 (e.g.,the CPU 150) determines the distance (i.e., depth) from each of theplurality of surface points in the region of interest to the referencesurface 250. In one embodiment, the video inspection device 100 (e.g.,the CPU 150) determines the distance of a line extending between thereference surface 250 and each of the plurality of surface points in theregion of interest 270, 280, wherein the line perpendicularly intersectsthe reference surface 250.

At step 360 of the exemplary method 300 (FIG. 3), the video inspectiondevice determines the location of the deepest surface point 224 in theregion of interest 270, 280 by determining the surface point that isfurthest from the reference surface 250 (e.g., selecting the surfacepoint with the longest line extending to the reference surface 250). Itwill be understood that, as used herein, the “deepest point” or “deepestsurface point” can be a furthest point that is recessed relative to thereference surface 250 or a furthest point (i.e., highest point) that isprotruding from the references surface 250. The video inspection device100 can identify the deepest surface point 224 in the region of interest270, 280 on the image by displaying, e.g., a cursor 234 (FIG. 5) orother graphic identifier 282 (FIG. 6) on the deepest surface point 224.In addition and as shown in FIGS. 5 and 6, the video inspection device100 can display the depth 290 (in inches or millimeters) of the deepestsurface point 224 in the region of interest 270, 280 on the image 200(i.e., the length of the perpendicular line extending from the deepestsurface point 224 to the reference surface 250. By automaticallydisplaying the cursor 234 or other graphic identifier 282 (FIG. 6) atthe deepest surface point 224 in the region of interest 270, 280, thevideo inspection device 100 reduces the time required to perform thedepth measurement and improves the accuracy of the depth measurementsince the user does not need to manually identify the deepest surfacepoint 224 in the anomaly 204.

Once the cursor 234 has been displayed at the deepest surface point 224in the region of interest 270, 280, the user can select that point totake and save a depth measurement. The user can also move the cursor 234within the region of interest 270, 280 to determine the depth of othersurface points in the region of interest 270, 280. In one embodiment,the video inspection device 100 (e.g., CPU 150) can monitor the movementof the cursor 234 and detect when the cursor 234 has stopped moving.When the cursor 234 stops moving for a predetermined amount of time(e.g., 1 second), the video inspection device 100 (e.g., the CPU 150)can determine the deepest surface point proximate to the cursor 234(e.g., a predetermined circle centered around the cursor 234) andautomatically move the cursor 234 to that position.

FIG. 7 is a graphical representation of an exemplary profile 370 of theobject surface 210 of the viewed object 202 shown in the image 200 ofFIG. 1. In this exemplary profile 370, the reference surface 250 isshown extending between two reference surface points 221, 222 and theirrespective reference surface cursors 231, 232. The location and depth290 of the deepest surface point 224 in the region of interest is alsoshown in the graphical representation. In another embodiment, a pointcloud view can also be used to show the deepest surface point 224.

FIG. 8 is another image 500 obtained by the video inspection device 100of the object surface 510 of a viewed object 502 having an anomaly 504in an exemplary embodiment of the invention. Once again, in thisexample, the anomaly 504 is shown as a dent, where material has beenremoved from the object surface 510 of the viewed object 502 in theanomaly 504 by damage or wear. It will be understood that the anomaly504 shown in this exemplary embodiment is just an example and that theinventive method applies to other types of irregularities (e.g., cracks,corrosion pitting, coating loss, surface deposits, etc.). Once the image500 is obtained, and the anomaly 504 is identified, the image 500 can beused to determine the dimensions of the anomaly 504 (e.g., height ordepth, length, width, area, volume, point to line, profile slice, etc.).In one embodiment, the image 500 used can be a two-dimensional image 500of the object surface 510 of the viewed object 502, including theanomaly 504.

FIG. 9 is a flow diagram of a method 600 for displayingthree-dimensional data for inspection of the object surface 510 of theviewed object 502 shown in the image 500 of FIG. 8 in an exemplaryembodiment of the invention. It will be understood that the stepsdescribed in the flow diagram of FIG. 9 can be performed in a differentorder than shown in the flow diagram and that not all of the steps arerequired for certain embodiments.

At step 610, and as shown in FIG. 8, the operator can use the videoinspection device 100 to obtain an image 500 of the object surface 510of a viewed object 502 having an anomaly 504 and display it on a videomonitor (e.g., an integral display 170 or external monitor 172). In oneembodiment, the image 500 can be displayed in a measurement mode of thevideo inspection device.

At step 620, the CPU 150 of the video inspection device 100 candetermine the three-dimensional coordinates (x_(iS1), z_(iS1), z_(iS1))in a first coordinate system of a plurality of surface points on theobject surface 510 of the viewed object 502, including the anomaly 504.In one embodiment, the video inspection device can generatethree-dimensional data from the image 500 in order to determine thethree-dimensional coordinates. As discussed above, several differentexisting techniques can be used to provide the three-dimensionalcoordinates of the points on the image 500 of the object surface 510(e.g., stereo, scanning systems, structured light methods such as phaseshifting, phase shift moiré, laser dot projection, etc.).

At step 630, and as shown in FIG. 8, an operator can use the joystick180 (or other pointing device (e.g., mouse, touch screen)) of the videoinspection device 100 to select a plurality of measurement points on theobject surface 510 of the viewed object 502 proximate the anomaly 504 toconduct a particular type of measurement. The number of measurementpoints selected is dependent upon the type measurement to be conducted.Certain measurements can require selection of two measurement points(e.g., length, profile), while other measurements can require selectionof three or more measurement points (e.g., point-to-line, area,multi-segment). In one embodiment and as shown in FIG. 8, a total offour measurement points 521, 522, 523, 524 are selected on the objectsurface 510 of the viewed object 502 proximate the anomaly 504 toconduct a depth measurement of the anomaly 504, with three of themeasurement points 521, 522, 523 selected on the object surface 510proximate the anomaly 504, and the fourth measurement point 524 selectedto be at the deepest point of the anomaly 504. In one embodiment, theplurality of measurement points 521, 522, 523, 524 on the object surface510 of the viewed object 502 can be selected by placing cursors 531,532, 533, 534 (or other pointing devices) on pixels 541, 542, 543, 544of the image 500 corresponding to the plurality of measurement points521, 522, 523, 524 on the object surface 510. In the exemplary depthmeasurement, the video inspection device 100 can determine thethree-dimensional coordinates in the first coordinate system of each ofthe plurality of measurement points 521, 522, 523, 524. It will beunderstood that the inventive method is not limited to depthmeasurements or measurements involving four selected measurement points,but instead applies to various types of measurements involving differentnumbers of points, including those discussed above.

At step 640, and as shown in FIG. 8, the CPU 150 of the video inspectiondevice 100 can determine a reference surface 550. In the exemplary depthmeasurement of the anomaly 504 shown in FIG. 8, the three-dimensionalcoordinates of three or more surface points proximate one or more of thethree measurement points 521, 522, 523 selected on the object surface510 proximate the anomaly 504 can be used to determine a referencesurface 550 (e.g., a plane). In one embodiment, the video inspectiondevice 100 can perform a curve fitting of the three-dimensionalcoordinates in the first coordinate system of the three measurementpoints 521, 522, 523 (x_(iM1), y_(iM1), z_(iM1)) to determine anequation for the reference surface 550 (e.g., for a plane) having thefollowing form:k _(0RS1) +k _(1RS1) ·x _(iRS1) +k _(2RS1) ·y _(iRS1) =z _(iRS1)  (2)where (x_(iRS1), y_(iRS1), z_(iRS1)) are coordinates of anythree-dimensional point in the first coordinate system on the definedreference surface 550 and k_(0RS1), k_(1RS1), and k_(2RS1) arecoefficients obtained by a curve fitting of the three-dimensionalcoordinates in the first coordinate system.

It should be noted that a plurality of measurement points (i.e., atleast as many points as the number of k coefficients) are used toperform the curve fitting. The curve fitting finds the k coefficientsthat give the best fit to the points used (e.g., least squaresapproach). The k coefficients then define the plane or other referencesurface 550 that approximates the three-dimensional points used.However, if more points are used in the curve fitting than the number ofk coefficients, when you insert the x and y coordinates of the pointsused into the plane equation (2), the z results will generally notexactly match the z coordinates of the points due to noise and anydeviation from a plane that may actually exist. Thus, the x_(iRS1) andy_(iRS1) can be any arbitrary values, and the resulting z_(iRS1) tellsyou the z of the defined plane at x_(iRS1), y_(iRS1). Accordingly,coordinates shown in these equations can be for arbitrary points exactlyon the defined surface, not necessarily the points used in the fittingto determine the k coefficients.

In another embodiment, there are only two measurement points selectedfor a particular measurement (e.g., length, profile), prohibiting theuse of curve fitting based only on the three-dimensional coordinates ofthose two measurement points since three points are needed to determinek_(0RS1), k_(1RS1), and k_(2RS1). In that case, the video inspectiondevice 100 can identify a plurality of pixels proximate each of thepixels of the image corresponding to a plurality of points on the objectsurface 510 proximate each of the measurement points, and determine thethree-dimensional coordinates of those points, enabling curve fitting todetermine a reference surface 550.

In one embodiment and as shown in FIG. 8, the video inspection device100 can determine the three-dimensional coordinates in the firstcoordinate system of a plurality of frame points 560 (x_(iF1), y_(iF1),z_(iF1)) forming a frame 562 (e.g., a rectangle) on the referencesurface 550 around the anomaly 504 and the measurement points 521, 522,523, 524, which can be used later to display the location of thereference surface 550.

Once the reference surface 550 is determined, in the exemplaryembodiment shown in FIG. 8, the video inspection device 100 can conducta measurement (e.g., depth) of the anomaly 504 by determining thedistance between the fourth measurement point 524 selected to be at thedeepest point of the anomaly 504 and the reference surface 550. Theaccuracy of this depth measurement is determined by the accuracy inselecting the plurality of measurement points 521, 522, 523, 524 on theobject surface 510 of the viewed object 502. In many instances asdiscussed previously, the contour of the anomaly 504 in the image 500 isdifficult to assess from the two-dimensional image and may be too smallor otherwise insufficient to reliably locate the plurality ofmeasurement points 521, 522, 523, 524. Accordingly, in many cases, anoperator will want further detail in the area of the anomaly 504 toevaluate the accuracy of the location of these measurement points 521,522, 523, 524. So while some video inspection devices 100 can provide apoint cloud view of the full image 500, that view may not provide therequired level of detail of the anomaly 504 as discussed previously. Inorder to provide a more meaningful view of the object surface 510 in thearea around the measurement points 521, 522, 523, 524 than offered by apoint cloud view of the three-dimensional data of the entire image 500,the inventive method creates a subset of the three-dimensional data inthe region of interest.

At step 650, the CPU 150 of the video inspection device 100 canestablish a second coordinate system different from the first coordinatesystem. In one embodiment, the second coordinate system can be based onthe reference surface 550 and the plurality of measurement points 521,522, 523, and 524. The video inspection device 100 can assign the originof the second coordinate system (x_(O2), y_(O2), z_(O2))=(0, 0, 0) to belocated proximate the average position 525 of the three-dimensionalcoordinates of points on the reference surface 550 corresponding to twoor more of the plurality of measurement points 521, 522, 523, 524 on theobject surface 510 (e.g., by projecting the measurement points 521, 522,523, and 524 onto the reference surface 550 and determining an averageposition 525 on the reference surface 550). In some cases, thethree-dimensional coordinates of the points on the reference surface 550corresponding to the measurement points 521, 522, 523 can be the same.However, in some circumstances, due to noise and/or small variations inthe object surface 510, the measurement points 521, 522, 523 do not fallexactly on the reference surface 550, and therefore have differentcoordinates.

When determining points on the reference surface 550 that correspond tomeasurement points 521, 522, 523, 524 on the object surface 510, it isconvenient to apply the concept of line directions, which convey therelative slopes of lines in the x, y, and z planes, and can be used toestablish perpendicular or parallel lines. For a given line passingthrough two three-dimensional coordinates (x1, y1, z1) and (x2,y2,z2),the line directions (dx, dy, dz) may be defined as:dx=x2−x1  (3)dy=y2−y1  (4)dz=z2−z1  (5)

Given a point on a line (x1, y1, z1) and the line's directions (dx, dy,dz), the line can be defined by:

$\begin{matrix}{\frac{\left( {x - {x\; 1}} \right)}{dx} = {\frac{\left( {y - {y\; 1}} \right)}{dy} = \frac{\left( {z - {z\; 1}} \right)}{dz}}} & (6)\end{matrix}$

Thus, given any one of an x, y, or z coordinate, the remaining two canbe computed. Parallel lines have the same or linearly scaled linedirections. Two lines having directions (dx1, dy1, dz1) and (dx2, dy2,dz2) are perpendicular if:dx1·dx2+dy1·dy2+dz1·dz2=0  (7)

The directions for all lines normal to a reference plane defined usingequation (2) are given by:dx _(RSN) =−k _(1RS)  (8)dy _(RSN) =−k _(2RS)  (9)dz_(RSN)=1  (10)

Based on equations (6) and (8) through (10), a line that isperpendicular to the reference surface 550 and passing through a surfacepoint (x_(S), y_(S), z_(S)) can be defined as:

$\begin{matrix}{\frac{x - x_{S}}{- k_{1\;{RS}}} = {\frac{y - y_{S}}{- k_{2\;{RS}}} = {z - z_{S}}}} & (11)\end{matrix}$

In one embodiment, the coordinates of a point on the reference surface550 (x_(iRS1), y_(iRS1), z_(iRS1)) corresponding to a point on theobject surface 510 (x_(iS1), y_(iS1), z_(iS1)) (e.g. three-dimensionalcoordinates in a first coordinate system of points on the referencesurface 550 corresponding to the measurement points 521, 522, 523, 524),can be determined by defining a line normal to the reference surface 550having directions given in equations (8)-(10) and passing through(x_(iS1), y_(iS1), z_(iS1)), and determining the coordinates of theintersection of that line with the reference surface 550. Thus, fromequations (2) and (11):

$\begin{matrix}{z_{iRS} = \frac{\left( {{k_{1\;{RS}}^{2} \cdot z_{{iS}\; 1}} + {k_{1\;{RS}} \cdot x_{{iS}\; 1}} + {k_{2\;{RS}}^{2} \cdot z_{{iS}\; 1}} + {k_{2\;{RS}} \cdot y_{{iS}\; 1}} + k_{ORS}} \right)}{\left( {1 + k_{1\;{RS}}^{2} + k_{2\;{RS}}^{2}} \right)}} & (12)\end{matrix}$x _(iRS1) =k _(1RS1)·(z _(iS1) −z _(iRS1))+x _(iS1)  (13)y _(iRS1) =k _(2RS)·(z _(iS1) −z _(iRS1))+y _(iS1)  (14)

In one embodiment, these steps (equations (3) through (14)) can be usedto determine the three-dimensional coordinates of points on thereference surface 550 corresponding to the measurement points 521, 522,523, 524. Then the average position 525 of these projected points of themeasurement points on the reference surface 550 (x_(M1avg), y_(M1avg),z_(M1avg)) can be determined. The origin of the second coordinate system(x_(O2), y_(O2), z_(O2))=(0, 0, 0) can then be assigned and locatedproximate the average position 525 (x_(M1avg), y_(M1avg), z_(M1avg)).

Locating the origin of the second coordinate system proximate theaverage position 525 in the area of the anomaly 504 with the z valuesbeing the perpendicular distance from each surface point to thereference surface 550 allows a point cloud view rotation to be about thecenter of the area of the anomaly 504 and permits any depth map colorscale to indicate the height or depth of a surface point from thereference surface 550.

In order to take advantage of this second coordinate system, at step660, the CPU 150 of the video inspection device 100 transforms thethree-dimensional coordinates in the first coordinate system (x_(i1),y_(i1), z_(i1)) determined for various points (e.g., the plurality ofsurface points, the plurality of measurement points 521, 522, 523, 524,the points on the reference surface 550 including the frame points 560,etc.) to three-dimensional coordinates in the second coordinate system(x_(i2), y_(i2), z_(i2)).

In one embodiment, a coordinate transformation matrix ([T]) can be usedto transform the coordinates according to the following:([x _(i1) y _(i1) z _(i1) ]−[x _(M1avg) y _(M1avg) z _(M1avg)])*[T]=[x_(i2) y _(i2) z _(i2)]  (15)where [T] is a transformation matrix.

In non-matrix form, the three-dimensional coordinates in the secondcoordinate system can be determined by the following:x _(i2)=(x _(i1) −x _(M1avg))*T ₀₀+(y _(i1) −y _(M1avg))*T ₁₀+(z _(i1)−z _(M1avg))*T ₂₀  (16)y _(i2)=(x _(i1) −x _(M1avg))*T ₀₁+(y _(i1) −y _(M1avg))*T ₁₁+(z _(i1)−z _(M1avg))*T ₂₁  (17)z _(i2)=(x _(i1) −x _(M1avg))*T ₀₂+(y _(i1) −y _(M1avg))*T ₁₂+(z _(i1)−z _(M1avg))*T ₂₂  (18)where the transformation matrix values are the line direction values ofthe new x, y, and z axes in the first coordinate system.

At step 670, the CPU 150 of the video inspection device 100 determines asubset of the plurality of surface points that are within a region ofinterest on the object surface 510 of the viewed object 502. In oneembodiment, the region of interest can be a limited area on the objectsurface 510 of the viewed object 502 surrounding the plurality ofselected measurement points 521, 522, 523, 524 to minimize the amount ofthree-dimensional data to be used in a point cloud view. It will beunderstood that the step of determining of the subset 660 can take placebefore or after the transformation step 660. For example, if thedetermination of the subset at step 670 takes place after thetransformation step 660, the video inspection device 100 may transformthe coordinates for all surface points, including points that areoutside the region of interest, before determining which of those pointsare in the region of interest. Alternatively, if the determination ofthe subset at step 670 takes place before the transformation step 660,the video inspection device 100 may only need to transform thecoordinates for those surface points that are within the region ofinterest.

In one embodiment, the region of interest can be defined by determiningthe maximum distance (d_(MAX)) between each of the points on thereference surface 550 corresponding to the measurement points 521, 522,523, 524 and the average position 525 of those points on the referencesurface 550 (the origin of the second coordinate system (x_(O2), y_(O2),z_(O2))=(0, 0, 0) if done after the transformation, or (x_(M1avg),y_(M1avg), z_(M1avg)) in the first coordinate system if done before thetransformation). In one embodiment, the region of interest can includeall surface points that have corresponding points on the referencesurface 550 (i.e., when projected onto the reference surface) that arewithin a certain threshold distance (d_(ROI)) of the average position525 of the measurement points 521, 522, 523, 524 on the referencesurface 550 (e.g., less than the maximum distance (d_(ROI)=d_(MAX)) orless than a distance slightly greater (e.g. twenty percent greater) thanthe maximum distance (d_(ROI)=1.2*d_(MAX))). For example, if the averageposition 525 in the second coordinate system is at (x_(O2), y_(O2),z_(O2))=(0, 0, 0), the distance (d) from that position to a point on thereference surface 550 corresponding to a surface point (x_(iRS2),y_(iRS2), z_(iRS2)) is given by:d _(iRS2)=√{square root over ((x _(iRS2) −x _(O2))²+(y _(iRS2) −y_(O2))²)}  (19)

Similarly, if the average position 525 in the first coordinate system isat (x_(M1avg), y_(M1avg), z_(M1avg)), the distance (d) from thatposition to a point on the reference surface 550 corresponding to asurface point (x_(iRS1), y_(iRS1), z_(iRS1)) is given by:d _(iRS1)=√{square root over ((x _(iRS1) −x _(M1avg))²+(y _(iRS1) −y_(M1avg))²)}  (20)

If a surface point has a distance value (d_(iRS1) or d_(iRS2)) less thanthe region of interest threshold distance (d_(ROI)) and therefore in theregion of interest, the video inspection device 100 can write thethree-dimensional coordinates of that surface point and the pixel colorcorresponding to the depth of that surface point to a point cloud viewfile. In this exemplary embodiment, the region of interest is in theform of a cylinder that includes surface points falling within theradius of the cylinder. It will be understood that other shapes andmethods for determining the region of interest can be used.

The region of interest can also be defined based upon the depth of theanomaly 504 on the object surface 510 of the viewed object 502determined by the video inspection device 100 in the first coordinatesystem. For example, if the depth of the anomaly 504 was measured to be0.005 inches (0.127 mm), the region of interest can be defined toinclude only those points having distances from the reference surface550 (or z dimensions) within a certain range (±0.015 inches (0.381 mm))based on the distance of one or more of the measurement points 521, 522,523, 524 to the reference surface 550. If a surface point has a depthvalue inside the region of interest, the video inspection device 100 canwrite the three-dimensional coordinates of that surface point and thepixel color corresponding to the depth of that surface point to a pointcloud view file. If a surface point has a depth value outside of theregion of interest, the video inspection device 100 may not include thatsurface point in a point cloud view file.

At step 680, and as shown in FIG. 10, the monitor 170, 172 of the videoinspection device 100 can display a rendered three-dimensional view(e.g., a point cloud view) 700 of the subset of the plurality of surfacepoints in the three-dimensional coordinates of the second coordinatesystem, having an origin 725 at the center of the view. In oneembodiment (not shown), the display of the point cloud view 700 caninclude a color map to indicate the distance between each of the surfacepoints and the reference surface 750 in the second coordinate system(e.g., a first point at a certain depth is shown in a shade of redcorresponding that depth, a second point at a different depth is shownin a shade of green corresponding to that depth). The displayed pointcloud view 700 can also include the location of the plurality ofmeasurement points 721, 722, 723, 724. To assist the operator in viewingthe point cloud view 700, the video inspection device 100 can alsodetermine three-dimensional line points 771, 772, 773 along straightlines between two or more of the plurality of measurement points 721,722, 723 in the three-dimensional coordinates of the second coordinatesystem, and display those line points 771, 772, 773 in the point cloudview 700. The point cloud view 700 can also include a depth line 774from the measurement point 724 intended to be located at the deepestpoint of the anomaly 504 to the reference surface 750. In oneembodiment, the video inspection device 100 can determine if the depthline 774 exceeds a tolerance specification or other threshold andprovide a visual or audible indication or alarm of such an occurrence.

The displayed point cloud view 700 can also include a plurality of framepoints 760 forming a frame 762 on the reference surface 750 in thesecond coordinate system to indicate the location of the referencesurface 750. In another embodiment, the displayed point cloud view 700can also include a scale indicating the perpendicular distance from thereference surface 750.

As shown in FIG. 10, by limiting the data in the point cloud view 700 tothose points in the region of interest and allowing the view to berotated about a point 725 in the center of the region of interest (e.g.,at the origin), the operator can more easily analyze the anomaly 504 anddetermine if the depth measurement and placement of the measurementpoints 721, 722, 723, 724 was accurate. In one embodiment, the operatorcan alter the location of one or more of the measurement points 721,722, 723, 724 in the point cloud view 700 if correction is required.Alternatively, if correction is required, the operator can return to thetwo-dimensional image 500 of FIG. 8 and reselect one or more of themeasurement points 521, 522, 523, 524, and repeat the process.

In another embodiment, the monitor 170, 172 of the video inspectiondevice 100 can display a rendered three-dimensional view 700 of thesubset of the plurality of surface points in the three-dimensionalcoordinates of the first coordinate system without ever conducting atransformation of coordinates. In this embodiment, the point cloud view700 based on the original coordinates can also include the variousfeatures described above to assist the operator, including displaying acolor map, the location of the plurality of measurement points,three-dimensional line points, depth lines, frames, or scales.

FIG. 11 is a flow diagram of an exemplary method 800 for displaying atwo-dimensional image of viewed object simultaneously with an imagedepicting the three-dimensional geometry of the viewed object in anotherexemplary embodiment. It will be understood that the steps described inthe flow diagram of FIG. 11 can be performed in a different order thanshown in the flow diagram and that not all of the steps are required forcertain embodiments.

At step 810 of the exemplary method (FIG. 8), and as shown in FIG. 12,the video inspection device 100 (e.g., the imager 124 of FIG. 1) obtainsat least one two-dimensional image 903 of the object surface 911 of aviewed object 910 having an anomaly 912 and displays it on a first side901 of the display 900 (e.g., an integral display 170, external monitor172, or touch screen of a user interface). In one embodiment, thetwo-dimensional image 903 is displayed in a measurement mode of thevideo inspection device 100.

At step 820 of the exemplary method 800 (FIG. 11), and as shown in FIG.12, the video inspection device 100 (e.g., the CPU 150 of FIG. 1)determines the three-dimensional coordinates (e.g., (x, y, z)) of aplurality of surface points 913, 914 on the object surface 911 of theviewed object 910. In one embodiment, the video inspection devicegenerates three-dimensional data from the two-dimensional image 903 inorder to determine the three-dimensional coordinates. FIG. 12 is adisplay 900 of a two-dimensional first stereo image 903 of the viewedobject 910 on the first side 901 of the display 900, and a correspondingtwo-dimensional second stereo image 904 of the viewed object 910 on thesecond side 902 of the display 900. In one embodiment, the videoinspection device 100 (e.g., the CPU 150) employs stereo techniques todetermine the three-dimensional coordinates (e.g., (x, y, z)) of aplurality of surface points 913, 914 on the two-dimensional first stereoimage 903 by finding matching surface points 915, 916 on thecorresponding two-dimensional second stereo image 904 and then computingthe three-dimensional coordinates based on the pixel distance disparitybetween the plurality of surface points 913, 914 on the two-dimensionalfirst stereo image 903 (or an area of pixels (e.g., 4×4 area)) and thematching surface points 915, 916 on the corresponding two-dimensionalsecond stereo image 904. It will be understood and as shown in FIGS.12-14, the reference herein to a two-dimensional image with respect tostereo image 903, 904 can include both or either of the first (left)stereo image 903 and the second (right) stereo image 904.

Several different existing techniques can be used to provide thethree-dimensional coordinates of the surface points 913, 914 in thetwo-dimensional image 903 (FIG. 12) of the object surface 911 (e.g.,stereo, scanning systems, stereo triangulation, structured light methodssuch as phase shift analysis, phase shift moiré, laser dot projection,etc.). Most such techniques comprise the use of calibration data, which,among other things, includes optical characteristic data that is used toreduce errors in the three-dimensional coordinates that would otherwisebe induced by optical distortions. With some techniques, thethree-dimensional coordinates may be determined using one or moretwo-dimensional images captured in close time proximity that may includeprojected patterns and the like. It is to be understood that referencesto three-dimensional coordinates determined using two-dimensional image903 may also comprise three-dimensional coordinates determined using oneor a plurality of two-dimensional images of the object surface 911captured in close time proximity, and that the two-dimensional image 903displayed to the operator during the described operations may or may notactually be used in the determination of the three-dimensionalcoordinates.

At step 830 of the exemplary method 800 (FIG. 11), and as shown in FIGS.13 and 14, at least a portion of the two-dimensional image 903 of theviewed object 910 with measurement cursors 931, 932 is displayed on afirst side 901 of the display 900 and a rendered image 905 of thethree-dimensional geometry of at least a portion of the object surface911 of the viewed object 910 is displayed on the second side 902 of thedisplay 900. As compared to FIG. 12, the rendered image 905 replaces thesecond (right) stereo image 904 in the display 900. In one embodiment,the video inspection device 100 (e.g., the CPU 150) begins (and, in oneembodiment, completes) the process of determining the three-dimensionalcoordinates (e.g., (x, y, z)) of the plurality of surface points 913,914 on the object surface 911 of the viewed object 910 before theplacement and display of the measurement cursors 931, 932. Although theexemplary embodiments shown in FIGS. 13 and 14 show a single renderedimage 905 of the three-dimensional geometry of the object surface 911 ofthe viewed object 910 displayed on the second side 902 of the display900, it will be understood that more than one rendered image 905 can beshown simultaneously with or without the two-dimensional image 903.

In an exemplary embodiment shown in FIG. 13, the rendered image 905 is adepth profile image 906 showing the three-dimensional geometry of theobject surface 911 of the viewed object 910, including the anomaly 912.In another exemplary embodiment shown in FIG. 14, the rendered image 905is a point cloud view 907 showing the three-dimensional geometry of theobject surface 911 of the viewed object 910, including the anomaly 912.In the exemplary point cloud view 907 shown in FIG. 14, only a subset ofthe three-dimensional coordinates of the surface points 913, 914 on theobject surface 911 of the viewed object 910 are displayed in a region ofinterest based on the location of the measurement cursors 931, 932. Inanother embodiment, the point cloud view 907 displays all of thecomputed three-dimensional coordinates of the surface points 913, 914 onthe object surface 911 of the viewed object 910. In one embodiment,e.g., when the display is a user-interface touch screen, the user canrotate the point cloud view 907 using the touch screen.

In one embodiment and as shown in FIG. 14, the point cloud view 907 maybe colorized to indicate the distance between the surface points of theobject surface 911 of the viewed object 910 and a reference surface 960(e.g., reference plane determined using three-dimensional coordinatesproximate to one or more of the plurality of measurement cursors 931,932). For example, a first point at a certain depth is shown in a shadeof red corresponding that depth, a second point at a different depth isshown in a shade of green corresponding to that depth. A color depthscale 908 is provided to show the relationship between the colors shownon the point cloud view 907 and their respective distances from thereference surface 960. In one embodiment, the point could view 907 maybe surfaced to graphically smooth the transition between adjacent pointsin the point cloud view 907.

Once the three-dimensional coordinates have been determined for aplurality of surface points 913, 914 on the object surface 911 of theviewed object 910, the user can conduct measurements on thetwo-dimensional image 903.

In one embodiment, the video inspection device 100 saves as an image thesplit view of the two-dimensional image 903 and the rendered image 905.The video inspection device 100 can also save as metadata the original,full stereo image of the first (left) stereo image 903 and the second(right) stereo image 904 (e.g., grayscale only) as shown in FIG. 11 andthe calibration data to allow re-computation of the three-dimensionaldata and re-measurement from the saved file. Alternatively, the videoinspection device 100 can save the computed three-dimensionalcoordinates and/or disparity data as metadata, which reduces theprocessing time upon recall but results in a larger file size.

At step 840 of the exemplary method 800 (FIG. 11), and as shown in FIGS.13 and 14, measurement cursors 931, 932 are placed (using a pointingdevice) and displayed on the two-dimensional image 903 to allow thevideo inspection device 100 (e.g., the CPU 150) to determine thedimensions of the anomaly 912 (e.g., height or depth, length, width,area, volume, point to line, profile slice, etc.). In another embodimentwhere the two-dimensional image is not a stereo image, measurementcursors 931, 932 (as shown in FIGS. 13 and 14) can also be placed on thetwo-dimensional image 903 to allow the video inspection device 100(e.g., the CPU 150) to determine the dimensions of the anomaly 912(e.g., height or depth, length, width, area, volume, point to line,profile slice, etc.). In yet another embodiment, instead of being placedon the two-dimensional image 903, measurement cursors can be placed(using a pointing device) on the rendered image 905 of thethree-dimensional geometry of at least a portion of the object surface911 of the viewed object 910 on the second side 902 of the display 900.

In the exemplary display 900, the first measurement cursor 931 is placedon the first measurement point 921 on the object surface 911 of theviewed object 910 and the second measurement cursor 932 is placed on thesecond measurement point 922 on the object surface 911 of the viewedobject 910. Since the three-dimensional coordinates of the measurementpoints 921, 922 on the object surface 911 of the viewed object 910 areknown, a geometric measurement (e.g., depth or length measurement) ofthe object surface 911 can be performed by the user and the videoinspection device 100 (e.g., the CPU 150) can determine the measurementdimension 950 as shown in FIGS. 13 and 14. In the example shown in FIGS.13 and 14, a measurement line 933 is displayed on the two-dimensionalimage 903.

The rendered image 905 of the three-dimensional geometry of the objectsurface 911 of the viewed object 910 is displayed on the second side 902of the display 900 in order to assist in the placement of themeasurement cursors 931, 932 on the two-dimensional image 903 to conductthe geometric measurement. In a conventional system involving stereo ornon-stereo two-dimensional images, these measurement cursors 931, 932(as shown in FIGS. 13 and 14) are placed based solely on the viewprovided by the two-dimensional image 903, which may not allow foraccurate placement of the measurement cursors 931, 932 and accuratemeasurements.

At step 850 of the exemplary method 800 (FIG. 11), and as shown in FIGS.13 and 14, measurement identifiers 941, 942 corresponding to themeasurement cursors 931, 932 placed on the two-dimensional image 903 aredisplayed on the rendered image 905 of the three-dimensional geometry ofthe object surface 911 of the viewed object 912. For example, the firstmeasurement identifier 941 is shown on the rendered image 905 at thesame three-dimensional coordinate of the object surface 911 of theviewed object 912 as the first measurement cursor 931, and the secondmeasurement identifier 942 is shown on the rendered image 905 at thesame three-dimensional coordinate of the object surface 911 of theviewed object 912 as the second measurement cursor 932. In the exemplarypoint cloud view 907 shown in FIG. 14, a measurement line identifier 943corresponding to the measurement line 933 (e.g., depth measurement line)in the two-dimensional image 901 is displayed. This rendered image 905of the three-dimensional geometry of the object surface 911 of theviewed object 910 simultaneously displayed with the two-dimensionalimage 903 of the object surface 911 of the viewed object 912 allows theuser to more accurately place the measurement cursors 931, 932 toprovide a more accurate geometric measurement. In yet anotherembodiment, where the measurement cursors are placed (using a pointingdevice) on the rendered image 905, measurement identifiers correspondingto the measurement cursors are displayed on the two-dimensional image903.

In one embodiment, as the user changes the location of the measurementcursors 931, 932 in the two-dimensional image 903, the video inspectiondevice 100 (e.g., the CPU 150) automatically updates the location of themeasurement identifiers 941, 942 corresponding to the measurementcursors 931, 932 and the rendered image 905 (e.g., region of interest ordepth colors of the point cloud view 907 in FIG. 14) of thethree-dimensional geometry of the object surface 911 of the viewedobject 912 also changes to allow the user to visualize the newmeasurement virtually in real time. In another embodiment, after themeasurement cursors 931, 932 are placed in the two-dimensional image903, the measurement identifiers 941, 942 can be repositioned in therendered image 905.

In yet another embodiment, where the measurement cursors are placed(using a pointing device) on the rendered image 905 and measurementidentifiers corresponding to the measurement cursors are displayed onthe two-dimensional image 903, as the user changes the location of themeasurement cursors in the rendered image 905, the video inspectiondevice 100 (e.g., the CPU 150) automatically updates the location of themeasurement identifiers corresponding to the measurement cursors and thetwo-dimensional image also changes to allow the user to visualize thenew measurement virtually in real time. In another embodiment, after themeasurement cursors are placed on the rendered image 905. themeasurement identifiers can be repositioned in the two-dimensional image903.

At step 860 of the exemplary method 800 (FIG. 11), and as shown in FIGS.13 and 14, the video inspection device 100 (e.g., the CPU 150)determines the measurement dimension 950 sought by the user for theparticular geometric measurement (e.g., depth or length measurement)based on the locations of the measurement cursors 931, 932 and displaysthat measurement dimension 950 on the display 900. In anotherembodiment, the measurement dimension can displayed on the display 900on the rendered image 905.

As shown in FIGS. 12-14, soft keys 909 can be provided on the display900 to provide various functions to the user in obtaining images andtaking measurements (e.g., views, undo, add measurement, nextmeasurement, options, delete, annotation, take image, reset, zoom, fullimage/measurement image, depth map on/off, etc.). In one embodiment,when a user activates either the two-dimensional image 903 or therendered image 905, the particular soft keys 909 displayed can changebased on the active image.

FIG. 15A is another exemplary image 1001 obtained by the videoinspection device 100 of a turbine blade 1010 having a missing corner(shown by polygon 1050) and a shroud 1015 in another exemplaryembodiment. In one embodiment, the image 1001 used can be atwo-dimensional image 1001 of the surface 1013 of the viewed object(turbine blade 1010). In a further example, the two-dimensional imagecan be a stereo image. As shown in FIG. 15A, the user can use the videoinspection device 100 (e.g., the imager 124) to obtain at least oneimage 1001 of the surface 1013 of the turbine blade 1010 and display iton a video monitor (e.g., an integral display 170 or external monitor172). In one embodiment, the image 1001 can be displayed in ameasurement mode of the video inspection device 100.

The video inspection device 100 (e.g., the CPU 150) can determine thethree-dimensional coordinates (e.g., (x, y, z)) of a plurality ofsurface points on the object surface 1013 of the viewed object 1010. Inone embodiment, the video inspection device can generatethree-dimensional data from the image 1001 in order to determine thethree-dimensional coordinates. The three-dimensional coordinates of thesurface points on the object surface 1013 of the viewed object 1010 canbe associated with the pixels of the displayed two-dimensional image1001. Several different existing techniques can be used to provide thethree-dimensional coordinates of the surface points in the image 1001(FIG. 15A) of the object surface 1013 (e.g., stereo, scanning systems,stereo triangulation, structured light methods such as phase shiftanalysis, phase shift moiré, laser dot projection, etc.). In oneembodiment, the video inspection device 100 captures the two-dimensionalimage 1001 using a diffuse inspection light source with no structuredlight pattern and the three-dimensional surface coordinates are computedusing one or more images captured with a structured light patternprojected onto the object. In such a case, the structured light patternmay be projected with the diffuse inspection light source disabled.

Once again, most such techniques comprise the use of calibration data,which, among other things, includes optical characteristic data that isused to reduce errors in the three-dimensional coordinates that wouldotherwise be induced by optical distortions. With some techniques, thethree-dimensional coordinates may be determined using one or more imagescaptured in close time proximity that may include projected patterns andthe like. In one embodiment, video inspection device 100 (e.g., the CPU150) may use calibration data to compute the object surface pointcoordinates. In one example, calibration data may be specific to thevideo inspection device 100 is used, and may include sensor and opticsinformation needed to determine actual dimensions and distances. Inanother example, calibration data may include ray equations to correlateeach pixel of the sensor with a specific point on the viewed object.

It is to be understood that references to three-dimensional coordinatesdetermined using image 1001 may also comprise three-dimensionalcoordinates determined using one or a plurality of images 1001 of theobject surface 1013 captured in close time proximity, and that the image1001 displayed to the user during the described operations may or maynot actually be used in the determination of the three-dimensionalcoordinates. In one embodiment, the video inspection device 100 (e.g.,the CPU 150) may average together multiple captured images in order togenerate a composite image with enhanced detail or reduced noise ascompared with a single image.

As shown in FIG. 15A, the video inspection device 100 (e.g., the CPU150) can determine a three-dimensional reference surface 1020 (e.g.,measurement plane shown by dashed lines extending across the image). Insome embodiments, the reference surface 1020 can be flat, while in otherembodiments the reference surface 1020 can be curved. Similarly, in oneembodiment, the reference surface 1020 can be in the form of a plane,while in other embodiments, the reference surface 1020 can be in theform of a different shape (e.g., cylinder, sphere, etc.). For example, auser can use the joystick 180 (or other pointing device (e.g., mouse,touch screen)) of the video inspection device 100 to select one or morereference surface points 1021, 1022, 1023 on the image 1001 of theobject surface 1013 of the viewed object 1010 (turbine blade).

In one embodiment and as shown in FIG. 15A, a total of three referencesurface points 1021, 1022, 1023 are selected on the image 1001 of theobject surface 1013 of the viewed object 1010. In one embodiment, theplurality of reference surface points 1021, 1022, 1023 on the objectsurface 1013 of the viewed object 1010 can be selected by placingreference surface cursors 1031, 1032, 1033 (or other pointing devices)on reference surface pixels 1041, 1042, 1043 of the image 1001corresponding to the plurality of reference surface points 1021, 1022,1023 on the object surface 1013. The video inspection device 100 (e.g.,the CPU 150) can determine the three-dimensional coordinates of each ofthe plurality of reference surface points 1021, 1022, 1023.

As shown in FIG. 15A, the CPU 150 of the video inspection device 100 candetermine a reference surface 1020. In the exemplary area measurementshown in FIG. 15A, the three-dimensional coordinates of the threereference surface points 1021, 1022, 1023 or three or more surfacepoints proximate one or more of the three reference surface points 1021,1022, 1023 can be used to determine a reference surface 1020 (e.g., aplane). As discussed above, in one embodiment, the video inspectiondevice 100 can perform a curve fitting of the three-dimensionalcoordinates of the three reference surface points 1021, 1022, 1023 todetermine an equation for the reference surface 1020 (e.g., for a planeextending indefinitely in all directions). In one embodiment, the videoinspection device 100 (e.g., the CPU 150) can perform a curve fitting ofthe three-dimensional coordinates of the surface points associated withthe pixels in the vicinity of reference surface cursors 1031, 1032, 1033to determine an equation for the reference surface 1020 (e.g., for aplane) as described in equation (1) above. In another embodiment, thecurve fitting may use only the three-dimensional coordinates of thesurface points associated with the pixels in the vicinity of only one ofthe reference surface cursors 1031, 1032, 1033 for the reference surface1020. In another embodiment, the three-dimensional coordinates of asingle selected reference surface point can be used by the videoinspection device 100 (e.g., the CPU 150) to establish the referencesurface to be a plane at z=10 mm (the z axis being along the centraloptical axis of the borescope view). In another example, a single cursormay be used to define a reference surface, for example, by establishinga plane orthogonal or parallel to the surface or the principal axis ofthe viewing optical system and passing through the three-dimensionalsurface coordinate associated with the cursor location. In a furtherexample, four or more selected coordinates can establish various curvedreference surfaces, such as spherical, cylindrical, or other surfaceshapes, as the reference surface. In further examples, numerous cursorsmay be used to fit curved surfaces, such as spheres, cylinders, etc. Inanother embodiment, one or more cursors may be used to select regions ofpixels, i.e. the region within a circular cursor, and the referencesurface may be determined by fitting a plane or other surface to thethree-dimensional surface coordinates associated with the selectedregion or regions.

As shown in FIG. 15A, the turbine blade 1010 has a missing corner (shownby polygon 1050). The present disclosure provides methods and devicesfor measuring features on or near an object, including features that mayhave portions that are missing or spaced apart from the object. Forinstance, a turbine blade 1010 may be inspected to determine if the tipor corner of the blade 1010 has broken off. In such a case, the relevantfeature to be measured, e.g., dimensions of the missing corner, is noton the surface 1013 of the turbine blade 1010 itself, and insteadextends into space beyond the surface 1013 of the turbine blade 1010.Therefore, a measurement using only the three-dimensional coordinates ofthe points on the surface 1013 of the turbine blade 1010 would notprovide the desired information (missing area, lengths of the missingedges, etc.). As will be explained, once the reference surface 1020 isestablished, the user may perform a measurement of a geometricdimension, such as a length, point to line, area, or multi-lengthmeasurement, by positioning measurement cursors 1034, 1035, 1036, 1037on the image 1001 even in areas that are not on the surface of theviewed object 1010 that do not have surface points on the surface 1013of the turbine blade 1010 associated with them.

In one embodiment and as shown in FIG. 15A, a total of four measurementcursors 1034, 1035, 1036, 1037 are positioned on measurement cursorpixels 1044, 1045, 1046, 1047 of the image 1001. As will be explained,through calibration, the three-dimensional trajectory associated witheach two-dimensional measurement cursor pixel 1044, 1045, 1046, 1047 ofthe image 1001 is known and used to calculate where the trajectory linefrom each measurement cursor pixel 1044, 1045, 1046, 1047 of the image1001 is positioned (e.g., which can be a fractional pixel position inwhich interpolation would be used) intersects with the reference surface1020 in three-dimensional space to determine the projected referencesurface points 1024, 1025, 1026, 1027 associated with those measurementcursor pixels 1044, 1045, 1046, 1047 on the reference surface 1020. Ascan be seen in FIG. 15A, once the projected reference surface points1024, 1025, 1026, 1027 on the reference surface 1020 are known, the usermay perform a measurement, such as a length, point to line, area, ormulti-length measurement, based on the three-dimensional coordinates ofthe projected reference surface points 1024, 1025, 1026, 1027 on thereference surface 1020. For example, as shown in FIG. 15A, the user canperform an area measurement forming a polygon 1050 having a first side1051 (which provides the length of missing portion of the first edge1011 of the blade), a second side 1052 (which provides the length ofmissing portion of the second edge 1012 of the blade), and a third side1053.

FIG. 15B is a display of a three-dimensional point cloud view 1002 ofthe turbine blade 1010 having a missing corner (shown by polygon 1050)and a shroud 1015 as shown in FIG. 15A in an another exemplaryembodiment. The three-dimensional point cloud view 1002 showing thethree-dimensional surface points of the turbine blade 1010, thereference surface 1020, and the projected reference surface points 1024,1025, 1026, 1027 allows the user to better visualize the measurement toensure that the measurement is being performed properly. As shown inFIG. 15B, the point cloud view 1002 may include the computedthree-dimensional surface coordinates on the viewed object 1010, whichmay be shown as individual points, a mesh, or a continuous surface. Thethree dimensional coordinates associated with measurement cursors 1034,1035, 1036, 1037 may be shown as dots, spheres or the like, andinterconnecting lines (polygon 1050 with sides 1051, 1052, 1053, 1054)outlining the feature (missing corner) may be included. The referencesurface 1020 and its location may also be represented by an additionalfeature, such as a rectangle or square. Thus, the three-dimensionalpoint cloud view 1002 allows the user to visualize the measurement inthree-dimensional space to ensure that it is being performed properly.Such an assessment can be very difficult to make using only atwo-dimensional image 1001. In one embodiment the three-dimensionalpoint cloud view 1002 is displayed simultaneously with thetwo-dimensional image 1001, and the three-dimensional point cloud view1002 is updated automatically when a measurement cursor is repositionedin the two-dimensional image 1001. In another embodiment the user mayselect to view either the two-dimensional image 1001 or thethree-dimensional point cloud view 1002 individually.

FIG. 15C is another exemplary image 1003 obtained by the videoinspection device 100 of a turbine blade 1010 having a missing corner inan another exemplary embodiment. In some cases, it may be useful to useboth three-dimensional coordinates of projected reference surface points(for points off of the viewed object) and three-dimensional coordinatesof surface points on the viewed object to perform a measurement. Withreference to FIG. 15C, an area measurement (polygon 170) may beperformed using reference surface 1020. In the illustrated embodiment,four measurement cursors 1071, 1072, 1073, 1074 may be selected, withtwo measurement cursors 1071, 1072 located on the surface 1013 of theviewed object 1010, and two measurement cursors 1073, 1074 located offthe surface 1013 of the viewed object 1010. The two measurement cursors1071, 1072 located on the surface 1013 of the viewed object 1010 arelocated on pixels associated with the three dimensional coordinates ofthe surface points on the on the surface 1013 of the viewed object 1010and the three-dimensional coordinates of the projected reference surfacepoints on the reference surface 1020. The two measurement cursors 1073,1074 located off the surface 1013 of the viewed object 1010 are locatedon pixels associated with the three dimensional coordinates of theprojected reference surface points on the reference surface 1020, butnot associated with the three dimensional coordinates of the surfacepoints on the surface 1013 of the viewed object 1010. The measurementmay utilize the three-dimensional coordinates of the surface pointslocated on the surface 1013 of the viewed object 1010 associated withthe two measurement cursors 1071, 1072 and the three-dimensionalcoordinates of the projected reference surface points on the referencesurface 1020 associated with the two measurement cursors 1073, 1074located off the surface 1013 of the viewed object 1010. Alternatively,the measurement may utilize the three-dimensional coordinates of theprojected reference surface points on the reference surface 1020associated with all four measurement cursors 1071, 1072, 1073, 1074. Inanother embodiment, the video inspection device 100 allows the user tochoose whether to use the three dimensional coordinates of the surfacepoints on the surface 1013 of the viewed object 1010 or thethree-dimensional coordinates of the projected reference surface pointson the reference surface 1020 for the two measurement cursors 1071, 1072located on the surface 1013 of the viewed object 1010. In one example,when measuring the gap between a turbine blade 1010 and the shroud 1015,a plane can be established on the shroud 1015 (using 3 cursors on pixelshaving associated three-dimensional coordinates), a measurement surfacecan be established on the blade 1010, a projected point on the edge ofthe blade 1010 is set using another cursor, and the perpendiculardistance from the plane to the point is computed.

FIG. 16 illustrates the relationship between image pixels, sensorpixels, reference surface coordinates, and object surface coordinates,in accordance with aspects set forth herein. For example, as describedbelow, pixels on a display 1101 may relate to pixels on a sensor 1102,which may relate, through ray equations, to a point C on the surface ofan object 1100. In the illustrated embodiment, a user may establish areference surface 1130 by choosing at least a point A on the surface ofobject 1100. For example, reference surface 1130 may be a planeintersecting with object 1100 at point A.

In one example, a user may desire to perform a measurement of a featureof object 1100 using reference surface 1130. In such a case, the usermay select a first pixel of the feature, pixel P_(D), on a display 1101by positioning a cursor on the two-dimensional image shown on thedisplay 1101. In such a case, pixel P_(D) on display 1101 may map topixel P_(S) on a sensor 1102, using, for example, the displayed imagepixel to captured image pixel conversion equations described below. Inaddition, pixel P_(S) on sensor 1102 may map to projectedthree-dimensional reference surface coordinate B on reference surface1130. In the illustrated example, pixel P_(S) on sensor 1102 may also beassociated with three-dimensional surface coordinate C on object 1100,which is a three-dimensional coordinate of the feature itself computedusing the captured images. Thus pixel P_(S) can have both an associatedthree-dimensional surface coordinate and a projected three-dimensionalreference surface coordinate, either of which may be used to compute ameasurement result. In one example, three-dimensional surface coordinateC is affected by three-dimensional data noise and therefore does notaccurately represent the surface of object 1100. In this case ameasurement result computed using projected three-dimensional referencesurface coordinate B may be more accurate than one computed usingcoordinate C. In another example, coordinate C may accurately representthe surface of object 1100, and the user may select to use coordinate Crather than coordinate B for use in computing the measurement result.

In certain implementations, a measurement system may include a sensorhaving a certain capture resolution, such as a 640×480 charge-coupleddevice (CCD). In addition, the measurement system may have a userinterface with a different display resolution, such as 1024×768 pixels.In such a case, when a user selects a cursor position on the userinterface screen, the selected screen pixel may be mapped to a sensorpixel. With reference to a pinhole camera model, for instance, if thedisplay resolution is 1024×768 and the capture resolution is 640×480,the capture column (col) and row may be calculated as follows:Capture col=Display col*640/1024=Display col*0.625Capture row=Display row*480/768=Display row*0.625

For example, a display cursor with {col, row}={15.33, 100.67} isequivalent to capture capture {col, row}={9.581, 62.919}. In such acase, bilinear interpolation may be used between capture pixels (9,62),(10,62), (9,63), (10,63), in order to interpolate the ray equations forthe equivalent pixel.

In one example, the ray equations are:x _(r,c)(z)=a _(r,c) *z and y _(r,c)(z)=b _(r,c) *z where a _(r,c) and b_(r,c) are pixel dependent.

In such a case, the interpolation coefficients may be calculated as:k _(c1)=col−(int)col=9.581−9=0.581k _(c0)=1−k _(c1)=0.419k _(r1)=row−(int)row=62.919−62=0.919k _(r0)=1−k _(r1)=0.081

a_(9.581,62.919)=k_(c0)*k_(r0)*a_(9.62)+k_(c1)*k_(r0)*a_(10.62)+k_(c0)*k_(r1)*a_(9.63)+k_(c1)*k_(r1)*a_(10.63)b _(9.581,62.919) =k _(c0) *k _(r0) *b _(9,62) +k _(c1) *k _(r0) *b_(10,62) +k _(c0) *k _(r1) *b _(9,63) +k _(c1) *k _(r1) *b _(10.63)

A similar bilinear interpolation approach may be used to determine anx,y,z surface coordinate associated with a displayed or captured imagepixel coordinate.

In one specific example, the ray equations may be used to map betweentwo-dimensional image pixels and reference surface coordinates asfollow.

The equation of a plane may be expressed as:z=z0+c*x+d*y

The equation of a ray may expressed as:x=a*z;y=b*z

In such a case, the intersection may be solved as follows:zi=z0+c*a*zi+d*b*zizi*(1−c*a−d*b)=z0zi=z0/(1−c*a−d*b)

For example, zi may be substituted into ray equations to get xi, yi.Thus, for a given two-dimensional displayed or captured image pixelcoordinate, an associated projected three-dimensional reference surfacecoordinate, xi, yi, zi, may be computed. For a given measurement, one ormore projected three-dimensional reference surface coordinatesassociated with one or more measurement cursor two-dimensional imagepixel coordinates are computed. The one or more projectedthree-dimensional reference surface coordinates are then used to computegeometric dimensions of a feature of a viewed object.

In view of the foregoing, embodiments of the invention allow formeasuring dimensions of features on or near the surface of an objectusing a video inspection system. A technical effect is to allow foraccurate measurements of object features where there is nothree-dimensional data or low accuracy three-dimensional data.

As shown in FIGS. 15A and 15C, common measurements performed by a videoinspection device 100 of a turbine blade 1010 having a missing cornerare the area of the missing corner, the length of missing portion 1051of the first edge 1011 of the blade 1010, and the length of missingportion 1052 of the second edge 1012 of the blade 1010. However, inorder to make the measurement on the reference plane 1020, a user has tovisually determine exactly where to place the measurement cursor 1037 atthe location where the tip or corner of the missing portion used to be,which can be difficult to extrapolate. In addition, if a user wants tofind the area of the missing corner and the two lengths 1051, 1052, theuser needs to place cursors to establish a reference surface and thenperform an area measurement and two point-to-line measurements,requiring several cursor placements. Furthermore, the point-to-linemeasurements provide lengths 1051, 1052 of the missing edge portionsthat assume a right angle corner, which is often not the case.

FIG. 17 is another exemplary image 1004 obtained by the video inspectiondevice 100 of a turbine blade 1010 having a missing corner in anotherexemplary embodiment. As will be explained, the video inspection device100 is able to detect when a missing corner area measurement is beingperformed and simplifies the measurement to automatically obtain thearea of the missing corner and the lengths 1051, 1052 of the missingedge portions. As explained above, in one embodiment and as shown inFIGS. 15A and 17, a total of three reference surface points 1021, 1022,1023 are selected on the image 1004 of the object surface 1013 of theviewed object 1010 by placing reference surface cursors 1031, 1032, 1033(or other pointing devices) on reference surface pixels 1041, 1042, 1043of the image 1001 corresponding to the plurality of reference surfacepoints 1021, 1022, 1023 on the object surface 1013. The CPU 150 of thevideo inspection device 100 can then determine a reference surface 1020as described above. The user can then select the option to perform anarea measurement.

In one embodiment and as shown in FIGS. 15A and 17, a total of fourmeasurement cursors 1034, 1035, 1036, 1037 are positioned on measurementcursor pixels 1044, 1045, 1046, 1047 of the image 1001. The videoinspection device 100 can then determine the projected reference surfacepoints 1024, 1025, 1026, 1027 associated with those measurement cursorpixels 1044, 1045, 1046, 1047 on the reference surface 1020.

In one embodiment, when the video inspection device 100 (e.g., CPU 150)determines a reference surface 1020 (e.g., measurement plane) anddetermines that the user is performing an area measurement as shown inFIGS. 15A and 17, the video inspection device 100 can then determine ifthe user is performing a missing corner measurement. For example, in oneembodiment, the video inspection device 100 (e.g., CPU 150) candetermine the total distance between each of the measurement cursors1034, 1035, 1036, 1037 and all three of the reference surface cursors1031, 1032, 1033 to identify the measurement cursor 1037 having thegreatest distance from the reference surface cursors 1031, 1032, 1033.The video inspection device 100 (e.g., CPU 150) can then determine theangle (α) between the two lines 1051, 1052 going to that measurementcursor 1037 in the area polygon 1050. If the angle (α) is in the rangebetween 45 degrees and 135 degrees, the video inspection device 100(e.g., CPU 150) determines that the user is conducting a missing cornermeasurement and automatically determines and displays in, e.g., a textbox 1083 the area, the angle (a), and lengths 1051 (A), 1052 (B) of themissing edge portions of the blade edges 1011, 1012. In addition, toassist the user in locating the measurement cursor 1037 at the locationwhere the tip or corner of the missing portion used to be, the videoinspection device 100 (e.g., CPU 150) determines and displays a firstedge line extension 1081 extending from the measurement cursor 1037along the turbine blade first edge 1011, and a second edge lineextension 1082 extending from the measurement cursor 1037 along theturbine blade second edge 1012 to provide a visual aid to the user toalign those edge line extensions 1081, 1082 with the turbine blade edges1011, 1012 to properly locate the measurement cursor 1037. As shown inFIG. 17, the first edge line extension 1081 and the second edge lineextension 1082 are straight lines in three-dimensional space whichappear as curved lines in the two-dimensional image 1004.

In view of the foregoing, embodiments of the invention allow formeasuring the dimension of a missing corner of the turbine blade using avideo inspection system. A technical effect is to allow for accuratemeasurements of the area and lengths of the missing corner using aminimum number of cursor placements, expediting the measurement.

Since the reference surface described herein is used to measure keydimensions in conducting inspections using various measurements relatingto the viewed object (e.g., depth, depth profile, or area depth profilemeasurement), it is important that the reference surface is properlyaligned with, and accurately represents, the physical object surface.Noise in the three-dimensional surface coordinates selected as referencesurface points can cause the reference surface to be tilted with respectto the actual surface causing poor accuracy of subsequent measurements.As will be discussed and as shown in FIGS. 19A and 19B, a visualindication, such as a semi-transparent visualization overlay 1240, 1280,can be placed on pixels in the two-dimensional image with associatedsurface points having three-dimensional surface coordinates less than apredetermined distance from the three-dimensional reference surface tohelp the user assess the matching between the reference surface and theobject surface. For example, pixels of the object proximate thereference surface may be highlighted (overlayed) in a contrasting color,such as green, to provide the visualization overlay. In another example,the video inspection device 100 displays on a three-dimensional pointcloud view an indication of which surface points have three dimensionalcoordinates that are less than a predetermined distance from thethree-dimensional reference surface that can also help the user assessthe matching between the reference surface and the object surface.Surface points of the object proximate the reference surface may bedefined by a Cartesian distance, or may be a simplified metric such asz-value distance to allow for ease of computation. FIGS. 19A and 19Billustrate techniques for marking an image with a visualization overlayto visualize a defined reference surface, such as a measurement plane.

FIG. 19A depicts a reference surface 1220 that is poorly aligned to theobject surface 1210. As shown in the image 1201 of the surface 1210 ofthe viewed object 1202 that includes an anomaly 1204, a referencesurface 1220 is established based on the placement of reference surfacecursors 1231, 1232, 1233 on the image 1201. A semi-transparentvisualization overlay 1240 is overlayed on pixels in the two-dimensionalimage 1201 with associated surface points having three-dimensionalsurface coordinates less than a predetermined distance from thethree-dimensional reference surface 1220. As shown in FIG. 19A, only asmall portion of the reference surface 1220 is covered by thevisualization overlay 1240, indicating that the reference surface 1220is tilted or otherwise not aligned well with the object surface 1210.Accordingly, measurements taken of the anomaly 1204 with that referencesurface 1220 would likely be inaccurate. The presence of thevisualization overlay 1240 would prompt the user to modify the referencecursor locations to find a better matching reference surface 1220 thathas better coverage by the visualization overlay 1240.

FIG. 19B depicts a well aligned reference surface 1260 where thereference surface 1260 is almost entirely covered with the visualizationoverlay 1280. As shown in the image 1241 of the surface 1250 of theviewed object 1242 that includes an anomaly 1244, a reference surface1260 is established based on the placement of reference surface cursors1271, 1272, 1273 on the image 1241. A semi-transparent visualizationoverlay 1280 is overlayed on pixels in the two-dimensional image 1241with associated surface points having three-dimensional surfacecoordinates less than a predetermined distance from thethree-dimensional reference surface 1260. As shown in FIG. 19A, theentire reference surface 1260 is covered by the visualization overlay1280 indicating that the reference surface 1260 is properly aligned withthe object surface 1250. Accordingly, measurements taken of the anomaly1244 with that reference surface 1260 would likely be accurate. Thepresence of the visualization overlay 1280 would inform the user thatthe cursor locations do not need to modified.

In one example, the visualization overlay may be updated in real time asthe cursors are moved by the user. In other examples, e.g., withmeasurement types such as depth profile and area depth profilemeasurements, the visualization overlay may be shown temporarily when acursor is moved and may be removed a few seconds after cursor movementstops. With depth measurements, the visualization overlay may bedisplayed whenever a reference surface cursor is active and may behidden if a 4^(th) cursor or the result is active. In another example,the visualization overlay may always be displayed whenever the referencesurface is active.

In order to determine whether to place a visualization overlay on apixel in the two-dimensional image, the video inspection device 100(e.g., CPU 150) determines if that pixel is associated with a surfacepoint having three-dimensional coordinates less than (or within) apredetermined distance from the three-dimensional reference surface. Insome embodiments, the distance between the surface point and thereference surface can be determined as a perpendicular distance, whilein other embodiments, the distance can be a non-perpendicular distance.

In one embodiment, a pixel can be included in the visualization overlayif its associated surface point is within a distance to the referencesurface of +/−1% of the surface point's z value. In one embodiment, thevideo inspection device 100 (e.g., CPU 150) can perform a coordinatetransformation such that the transformed z value for all points on thereference surface is z=0. Then for a given surface point, the videoinspection device 100 (e.g., CPU 150) can compare the actual(untransformed) z value of the surface point to the transformed z value.If the absolute value of the transformed z value (which provides theperpendicular distance from the reference surface) is less than 1% ofthe actual z value, the pixel associated with that surface point can beincluded in the visualization overlay.

In another embodiment not requiring a coordinate transformation, foreach pixel, the video inspection device 100 (e.g., CPU 150) candetermine a perpendicular projection onto the reference surface anddetermine the distance from the surface point to the reference surfacein a perpendicular direction. If that perpendicular distance is lessthan 1% of the actual z value, the pixel associated with that surfacepoint can be included in the visualization overlay. For example, if thedistance is 0.08 mm and the surface point has a z value of 10.0 mm, thepixel associated with that surface point can be included in thevisualization overlay.

In another embodiment not requiring a perpendicular distance, for eachpixel, the video inspection device 100 (e.g., CPU 150) can determine theactual z coordinate for the surface point and the z coordinate for thecorresponding projection point on the reference surface projected fromthat surface point, where such projection is not necessarily in aperpendicular direction. If the difference between the z value on thereference surface and the z value of the corresponding surface point isless than 1% of either z value, the pixel associated with that surfacepoint can be included in the visualization overlay.

In view of the foregoing, embodiments of the invention allow fordetermining whether a reference surface is properly aligned with, andaccurately represents, the physical object surface. A technical effectis to provide more accurate measurements involving the referencesurface.

In some instances, it can be difficult for a user to understand the tipof a probe of a visual inspection device is oriented relative to aninspected object when looking at the two-dimensional image or even apoint cloud view. For example, it may be difficult for a user tounderstand how to adjust the viewing perspective. FIG. 20 shows a fullimage point cloud view 1300 of an object 1310 displaying field of viewlines 1331, 1332, 1333, 1334 extending from the field of view origin1330 (0,0,0) to provide a visual indication of the orientation of thetip of the probe of the video inspection device 100 with respect to theobject 1310. As shown in FIG. 20, the reference surface 1320 and itslocation may also be represented by an additional feature, such as arectangle or square. In one embodiment, the user can turn the field ofview lines 1331, 1332, 1333, 1334 on or off as desired.

In some applications involving a reference surface as described herein,it may be desirable to make a measurement on the reference surface thatinvolves a feature that may include at least one surface point that isnot located on the reference surface and that may even be a significantdistance from the reference surface. When the reference surface is areference plane, such a measurement may be described as an in-planemeasurement to an out of plane surface point.

FIG. 21 shows a two dimensional image 1401 side-by-side with a pointcloud view 1402 of an object 1410 having an upper surface 1411 and alower surface 1412. As shown in FIG. 21, a reference surface 1420 isestablished based on the placement of reference surface cursors 1431,1432, 1433 on the image 1401. As explained above, through calibration,the three-dimensional trajectory associated with each pixel associatedwith each of the reference surface cursors 1431, 1432, 1433 is known andused to calculate where the trajectory line intersects with thereference surface 1420 in three-dimensional space to determine theprojected reference surface points 1424, 1425, 1426 on the referencesurface 1420. In one embodiment, a user may want to measure the distanceon the reference surface 1420 from a first edge 1413 between the uppersurface 1411 and the lower surface 1412 and a point of interest 1450 onthe lower surface 1412 that is not on the reference surface 1420. Thismeasurement can be performed using, e.g., a point-to-line measurementwith a first measurement line 1441 (the reference line) between thefirst measurement cursor 1434 (reference surface point 1424) and thesecond measurement cursor 1435 (second reference point 1425) and asecond measurement line 1442 between the first measurement line 1441(the reference line) and the third measurement cursor 1436 (referencesurface point 1426) positioned at a point on the reference surfacecorresponding to the location of the point of interest on the lowersurface 1412.

As can be seen in the image 1401 and point cloud view 1402 of FIG. 21,based on the viewing angle and the geometry of the object 1410, thethird measurement cursor 1436 (and corresponding reference surface point1426) is visually offset (i.e., not directly above or lined up visually)from the point of interest 1450 such that finding the correct locationof the third measurement cursor 1436 (and corresponding referencesurface point 1426) on the reference surface 1420 that corresponds tothe point of interest 1450 on the lower surface 1412 can be challenging.In order to assist the user, the video inspection device 100 (e.g., CPU150) can provide guide lines (e.g., guide line 1460) on the point cloudview 1402 to assist the user in placing the third measurement cursor1436.

In one embodiment, when a measurement is being performed involving areference surface 1420 (e.g., a measurement plane), the video inspectiondevice 100 (e.g., CPU 150) identifies points on the object surface(e.g., lower surface 1412) proximate (e.g., within 0.1 mm) lines thatare perpendicular to the reference surface 1420 and passing through theprojected reference surface point 1426 projected from the measurementcursor 1436. If such surface points are found, the video inspectiondevice 100 (e.g., CPU 150) provides a guide line 1460 in the point cloudview 1402 extending in a perpendicular direction from thethree-dimensional coordinate on the references surface 1420corresponding to the measurement cursor 1436 (or corresponding referencesurface point 1426). In one embodiment, a sphere is placed on thesurface point (e.g., point of interest 1450 as shown in the point cloudview 1402 of FIG. 21). This guide line 1460 helps the user position thethird measurement cursor 1436 on the reference surface 1420 in thetwo-dimensional image 1401 at the location corresponding to the point ofinterest 1450 to provide an accurate measurement. Accordingly, the usercan move the third measurement cursor 1436 in the two-dimensional image1401 until the guide line 1460 associated with that cursor 1436 contactsthe lower surface 1412 at the point of interest 1450. In one embodiment,the guide line 1460 may be optionally hidden or shown.

In some inspections with the video inspection device 100, a user needsto place measurement cursors at the edge of an object. For example, FIG.22A shows another two dimensional image 1501 side-by-side with a pointcloud view 1502 of an object (turbine blade 1510) in an exemplaryembodiment. As shown in FIG. 22A, the edge 1512 of the turbine blade1510 has a dent 1513 that may have been caused, e.g., by a stone orother foreign object passing through the turbine engine. In oneembodiment, where a user may want to measure the dimension of the dent1513, a user can position a first measurement cursor 1541 and a secondmeasurement cursor 1542 on the edge 1512 of the turbine blade 1510 and athird measurement cursor 1543 on the edge of the dent 1513. The threemeasurement cursors 1541, 1542, 1543 can be used to perform apoint-to-line measurement of the depth of the dent 1513 using a firstmeasurement line 1541 (the reference line) between the first measurementcursor 1541 and the second measurement cursor 1542 and a secondmeasurement line 1542 between the first measurement line 1541 (thereference line) and the third measurement cursor 1543. The length of thesecond measurement line 1542 provides the depth of the dent 1513.

In many cases, the three-dimensional coordinates for points on the edge1512 of the turbine blade 1510 are either not available or not highlyaccurate. Accordingly, as with the missing corner measurement describedabove, the point-to-line measurement of the dent 1513 can be performedon the reference surface (e.g., measurement plane). A reference surface1520 is established on the surface 1511 of the turbine blade 1510 basedon the placement of reference surface cursors 1531, 1532, 1533 on theimage 1501 where three-dimensional coordinates are available and highlyaccurate. Once the reference surface 1520 is established, thepoint-to-line measurement of the dent 1513 can be performed on referencesurface 1520 using the three-dimensional coordinates of the projectedreference surface points 1521, 1522, 1523 on the reference surface 1520associated with the measurement cursors 1541, 1542, 1543 as shown inFIGS. 22A and 22B.

The accuracy of this measurement is dependent on the accuracy of theuser's placement of the first measurement cursor 1541 and the secondmeasurement cursor 1542 on the actual edge 1512 of the turbine blade1510. For example, the measurement is dependent on the accuracy of theuser's placement of the first measurement cursor 1541 and the secondmeasurement cursor 1542 on the actual edge 1512 of the turbine blade1510 such that the projected reference surface points 1521, 1522 on thereference surface 1520 associated with the measurement cursors 1541,1542 accurately reflects the geometric location of the actual edge 1512of the turbine blade 1510. In many cases, the edge 1512 of the turbineblade 1510 is radiused or curved such that actual edge 1512 of theturbine blade 1510 curves away from the surface 1511 of the turbineblade 1510 and is not on the reference surface 1520 as shown in FIG.22A.

FIG. 22B shows the geometric relationship between an edge viewing angle(θ) of the video inspection device 100 and the reference surface 1520.As shown in FIGS. 22A and 22B, depending upon the edge viewing angle (θ)between the edge viewing angle line 1570 (or edge view plane 1572described below) from the origin 1560 (coordinates (0,0,0)) of the fieldof view (shown by field of view lines 1561, 1562, 1563, 1564) and thereference surface 1520 or the surface 1511 of the turbine blade 1510,the user unknowingly may not be able to see the actual edge 1512 of theturbine blade 1510 when trying to place the first measurement cursor1541 on the edge 1512 of the turbine blade 1510. For example, as shownin FIG. 22B, based on the edge viewing angle (θ), the user incorrectlyplaces the first measurement cursor 1541, which is intended to be placedon the actual edge 1512 of the turbine blade 1510, on a point on theturbine blade 1510 that is not the edge 1512. As shown in FIG. 22B,because of the inaccurate cursor placement, the distance (B) between theprojected reference surface points 1521, 1523 on the reference surface1520 associated with the measurement cursors 1541, 1543 (i.e., themeasured depth of the dent 1513) will be less than the actual depth (A)of the dent 1513 that would have been measured based on a correctprojected reference surface point 1571 that would have resulted if thefirst measurement cursor 1541 was placed on the actual edge 1512. Thiserror could possibly have been avoided if the edge viewing angle (θ)between the edge viewing angle line 1570 (or edge view plane 1572described below) and the reference surface 1520 or the surface 1511 ofthe turbine blade 1510 were closer to 90 degrees (or if the edge viewingangle (φ) between the edge viewing angle line 1570 (or edge view plane1572 described below) and a plane 1580 normal to the reference surface1520 or the surface 1511 of the turbine blade 1510 were closer to 0degrees).

In one embodiment and as shown in FIGS. 22A and 22B, the videoinspection device 100 can employ a warning system where a user is givena visual or audible warning when there is an undesirable (e.g., far fromperpendicular) viewing perspective at the location where a measurementcursor is being placed on an edge. In one embodiment involving apoint-to-line measurement or other measurement (area, length, depth,etc.) involving the edge 1512 of an object 1510 involving two or moremeasurement cursors 1541, 1542 placed along the edge 1512 of the object1510 to form a first measurement line 1551 (reference line), the videoinspection device 100 (e.g., CPU 150) uses edge detection to determinewhether either measurement cursor 1541, 1542 is located near an edge(e.g., the edge 1512 of the turbine blade 1510). If one or moremeasurement cursors 1541, 1542 are placed along the edge 1512, the videoinspection device 100 (e.g., CPU 150) can determine an edge view plane1572 based on the three-dimensional coordinates of the origin 1560 ofthe field of view (0,0,0) and the three-dimensional coordinatesassociated with the measurement cursors 1541, 1542 placed along the edge1511 of the turbine blade 1510. In one embodiment, as shown in FIG. 22B,the video inspection device 100 (e.g., CPU 150) then determines the edgeviewing angle (θ) between the edge view plane 1572 and the referencesurface 1520, which would ideally be 90 degrees (perpendicular) for thebest edge viewing angle for cursor placement on an edge. In anotherembodiment, the video inspection device 100 (e.g., CPU 150) determinesthe edge viewing angle (φ) between the edge view plane 1572 and a plane1580 normal to the reference surface 1520 and including thethree-dimensional coordinates associated with the measurement cursors1541, 1542 placed along the edge 1511 of the turbine blade 1510, whichwould ideally be 0 degrees (parallel) for the best edge viewing anglefor cursor placement on an edge. If the calculated edge viewing angle (θor φ) is outside of an acceptable range of angles or exceeds (or fallsbelow) a threshold) (e.g., if θ is less than 60 degrees or if φ isgreater than 30 degrees), then the video inspection device 100 candisplay a warning message 1503 to the user (e.g., “To improve accuracy,capture with a more perpendicular view at cursors near edges”). Theborder of the text box 1504 showing the measurement and edge viewingangle can be illuminated in warning color (orange) and flash to warn theuser. In addition, an edge view angle line 1570, which lies on the edgeview plane 1570 and is perpendicular to the first measurement line 1541(the reference line) can also be shown in a warning color (e.g., orange)on the point cloud view 1502. As shown in FIG. 22A, the point cloud view1502 includes field of view lines 1561, 1562, 1563, 1564 and arepresentation of the reference plane 1520 to assist the user inrepositioning the tip of the probe of the video inspection device toimprove the edge viewing angle for more accurate cursor placement.

In the exemplary point-to-line measurement shown in FIGS. 22A and 22B,in addition to the first measurement cursor 1541 and the secondmeasurement cursor 1542 being placed on the edge 1512 of the turbineblade 1510, the third measurement cursor 1543 is also placed along anedge of the dent 1513. Similarly, in FIGS. 17A and 17C, the third orfourth cursors involved in a measurement and offset from the first twomeasurement cursors may also be placed on another edge of the object. Inone embodiment, in addition to determining an edge view plane 1572 basedon the first two measurement cursors 1541, 1542 that form the firstmeasurement line 1551 (reference line), the video inspection device 100(e.g., CPU 150) can also determine whether the third measurement cursor1543 is near an edge and whether that edge is parallel or perpendicularto the first measurement line 1551 (reference line). The videoinspection device 100 (e.g., CPU 150) can determine a point view planebased on the three-dimensional coordinates of the origin 1560 of thefield of view (0,0,0) and the three-dimensional coordinates associatedwith the third measurement cursor 1543 and an additional point offsetfrom the third measurement cursor 1543 in a direction parallel orperpendicular to the first measurement line 1551 (reference line)depending on the direction of the detected edge. In one embodiment, thevideo inspection device 100 (e.g., CPU 150) then determines the pointviewing angle between the point view plane and the reference surface1520, which would ideally be 90 degrees (perpendicular) for the bestviewing angle for cursor placement on an edge. In another embodiment,the video inspection device 100 (e.g., CPU 150) determines the pointviewing angle between the point view plane and a plane normal to thereference surface 1520 and including the three-dimensional coordinatesassociated with the third measurement cursor 1543 and the additionalpoint offset from the third measurement cursor 1543, which would ideallybe 0 degrees (parallel) for the best viewing angle for cursor placementon an edge.

The video inspection device 100 (e.g., CPU 150) then determines aselected viewing angle between the edge viewing angle and the pointviewing angle, wherein the selected viewing angle is then used todetermine whether a warning needs to be provided. For example, if (i)none of the measurement cursors 1541, 1542, 1543 are near an edge or(ii) at least one of the first measurement cursor 1541 or the secondmeasurement cursor 1542 is near an edge and the third measurement cursor1543 is near an edge, the selected viewing angle is the larger of theedge viewing angle and the point viewing angle. If at least one of thefirst measurement cursor 1541 or the second measurement cursor 1542 isnear an edge, but the third measurement cursor 1543 is not, then theselected viewing angle is the edge viewing angle. If neither of thefirst measurement cursor 1541 or the second measurement cursor 1542 isnear an edge, but the third measurement cursor 1543 is near an edge,then the selected viewing angle is the point viewing angle. If theselected viewing angle (θ or φ) is outside of an acceptable range ofangles or exceeds (or falls below) a threshold), then the videoinspection device 100 can display a warning message 1503 to the user(e.g., “To improve accuracy, capture with a more perpendicular view atcursors near edges”). The border of the text box 1504 showing themeasurement and edge viewing angle can be illuminated in warning color(orange) and flash to warn the user.

In view of the foregoing, embodiments of the invention warn the userwhen the viewing angle is likely to produce inaccurate cursorplacements. A technical effect is to provide more accurate measurementsinvolving cursor placements.

In some situations, a user may desire to perform measurements on or nearturbines which may have blades with curved edge profiles. For instance,if damage occurs along the edge, the user may need to measure how far infrom the edge the damage extends. In addition, the user may also use agrinding tool and remove material from the edge around the damage. Insuch a case, the user may need to measure both the damage and grindingdepths from the original curved edge to ensure achievement of a profilethat will not have stress concentrations that could cause failure.Point-to-line measurements that do not account for the curvature of theblade edge cannot provide the desired information.

Advantageously, the techniques presented herein, may include the use ofreference profiles, go beyond point-to-line measurements, and are ableto account for the curvature of objects such as the blade edge of aturbine. In one embodiment a three-dimensional reference profile isdefined using points along the edge of an un-damaged blade and thenrecalled when measuring on an image of a damaged or repaired blade. Thisallows for measurements to be made from the curved original surface. Insuch a case, a reference surface is used to orient the reference profileto the face of the blade in three-dimensional space both when definingit and recalling it.

When the profile is recalled for use on a blade that has been damaged orblended (ground), the reference profile may be positioned to align withremaining unaltered edges of the blade in three-dimensional space. Thereare several ways this can be done. One example is to use thethree-dimensional coordinates associated with the reference surfacecursors to establish an alternate coordinate system in the originalimage in which the reference profile is defined and in the 2^(nd) imagein which it is recalled and then to use this alternate coordinate systemto define and then reconstruct the profile in three-dimensional space.Thus placing the reference surface cursors at the same locations on theblade in both images would position the recalled reference profile inthe same location and orientation in three-dimensional space relative tothe blade as it was in the first image in which it was definedregardless of changes in viewing position or angle.

Alternately, the recalled reference profile may be positioned directlyin the three-dimensional view. The position of the recalled referenceprofile can also be shown in the two-dimensional image by identifyingtwo-dimensional pixels that have pixel rays that pass within a maximumdistance of the recalled reference profile in three-dimensional space.In another embodiment, the three-dimensional coordinates defining thereference profile may be determined using a CAD model or physicalexample of the blade, which can then be imported and positioned to alignto the blade. In another embodiment, the system can store multiplereference profiles, and the user can recall one or more for use. Inanother embodiment, the system can compute geometric dimensions using arecalled reference profile. For example, the shortest distance betweenthe recalled reference profile and a user-designated three-dimensionalsurface coordinate or projected three-dimensional reference surfacecoordinate may be computed.

FIG. 18 shows a side by side two-dimensional/three-dimensional view of ameasurement plane (3 connected cursors) and a reference profile definedby the other 7 cursors. The reference profile uses three-dimensionalcubic spline fitting to better follow the curved edge profile with justa few cursors as is shown in the point cloud. In this case, thereference profile is defined using three-dimensional surfacecoordinates, though it could also be defined using projectedthree-dimensional measurement surface coordinates. The three-dimensionalsurface coordinates at the cursor locations can be saved to representthe reference profile.

As will be appreciated by one skilled in the art, aspects of the presentinvention may be embodied as a system, method, or computer programproduct. Accordingly, aspects of the present invention may take the formof an entirely hardware embodiment, an entirely software embodiment(including firmware, resident software, micro-code, etc.), or anembodiment combining software and hardware aspects that may allgenerally be referred to herein as a “service,” “circuit,” “circuitry,”“module,” and/or “system.” Furthermore, aspects of the present inventionmay take the form of a computer program product embodied in one or morecomputer readable medium(s) having computer readable program codeembodied thereon.

Any combination of one or more computer readable medium(s) may beutilized. The computer readable medium may be a computer readable signalmedium or a computer readable storage medium. A computer readablestorage medium may be, for example, but not limited to, an electronic,magnetic, optical, electromagnetic, infrared, or semiconductor system,apparatus, or device, or any suitable combination of the foregoing. Morespecific examples (a non-exhaustive list) of the computer readablestorage medium would include the following: an electrical connectionhaving one or more wires, a portable computer diskette, a hard disk, arandom access memory (RAM), a read-only memory (ROM), an erasableprogrammable read-only memory (EPROM or Flash memory), an optical fiber,a portable compact disc read-only memory (CD-ROM), an optical storagedevice, a magnetic storage device, or any suitable combination of theforegoing. In the context of this document, a computer readable storagemedium may be any tangible medium that can contain, or store a programfor use by or in connection with an instruction execution system,apparatus, or device.

Program code and/or executable instructions embodied on a computerreadable medium may be transmitted using any appropriate medium,including but not limited to wireless, wireline, optical fiber cable,RF, etc., or any suitable combination of the foregoing.

Computer program code for carrying out operations for aspects of thepresent invention may be written in any combination of one or moreprogramming languages, including an object oriented programming languagesuch as Java, Smalltalk, C++ or the like and conventional proceduralprogramming languages, such as the “C” programming language or similarprogramming languages. The program code may execute entirely on theuser's computer (device), partly on the user's computer, as astand-alone software package, partly on the user's computer and partlyon a remote computer or entirely on the remote computer or server. Inthe latter scenario, the remote computer may be connected to the user'scomputer through any type of network, including a local area network(LAN) or a wide area network (WAN), or the connection may be made to anexternal computer (for example, through the Internet using an InternetService Provider).

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems) and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer program instructions. These computer program instructions maybe provided to a processor of a general purpose computer, specialpurpose computer, or other programmable data processing apparatus toproduce a machine, such that the instructions, which execute via theprocessor of the computer or other programmable data processingapparatus, create means for implementing the functions/acts specified inthe flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in a computerreadable medium that can direct a computer, other programmable dataprocessing apparatus, or other devices to function in a particularmanner, such that the instructions stored in the computer readablemedium produce an article of manufacture including instructions whichimplement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions may also be loaded onto a computer,other programmable data processing apparatus, or other devices to causea series of operational steps to be performed on the computer, otherprogrammable apparatus or other devices to produce a computerimplemented process such that the instructions which execute on thecomputer or other programmable apparatus provide processes forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks.

To the extent that the claims recite the phrase “at least one of” inreference to a plurality of elements, this is intended to mean at leastone or more of the listed elements, and is not limited to at least oneof each element. For example, “at least one of an element A, element B,and element C,” is intended to indicate element A alone, or element Balone, or element C alone, or any combination thereof. “At least one ofelement A, element B, and element C” is not intended to be limited to atleast one of an element A, at least one of an element B, and at leastone of an element C.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they have structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal language of the claims.

What is claimed is:
 1. A method for measuring a feature on or near aviewed object, the method comprising the steps of: displaying on amonitor an image of the viewed object; determining the three-dimensionalcoordinates of a plurality of points on a surface of the viewed objectusing a central processor unit; selecting one or more reference surfacepoints from the plurality of points on the surface of the viewed objectusing a pointing device; determining a reference surface using thecentral processor unit, wherein the reference surface is determinedbased on the one or more of the reference surface points; placing one ormore measurement cursors on one or more measurement pixels of the imageusing a pointing device; determining one or more projected referencesurface points associated with the one or more measurement cursors onthe reference surface using the central processor unit, wherein each ofthe one or more projected reference surface points are determined basedon the intersection of a three-dimensional trajectory line from the oneor more measurement pixels and the reference surface; and determiningthe dimensions of the feature on or near the viewed object using thethree-dimensional coordinates of at least one of the one or moreprojected reference surface points using the central processor unit. 2.The method of claim 1, wherein the image of the viewed object is atwo-dimensional image.
 3. The method of claim 1, wherein the referencesurface is a plane.
 4. The method of claim 1, wherein the step ofselecting one or more reference surface points using a pointing deviceis performed by placing reference surface cursors on each of thereference surface points.
 5. The method of claim 1, further comprisingthe step of displaying on the monitor a three-dimensional view of theplurality of points on the surface of the viewed object and the one ormore projected reference surface points on the reference surface.
 6. Themethod of claim 1, wherein at least one of the one or more projectedreference surface points is associated with a measurement pixel nothaving associated three-dimensional coordinates of a point on thesurface of the viewed object.
 7. The method of claim 1, wherein at leastone of the one or more projected reference surface points is associatedwith a measurement pixel having associated three-dimensional coordinatesof a point on the surface of the viewed object.
 8. The method of claim7, wherein the step of determining the dimensions of the feature on ornear the viewed object using the three-dimensional coordinates of atleast one of the one or more projected reference surface points furthercomprises using the three-dimensional coordinates of at least one of theplurality of points on the surface of the viewed object.
 9. The methodof claim 1, wherein the reference surface is determined based on thethree-dimensional coordinates of the one or more of the referencesurface points or the three-dimensional coordinates of surface pointsproximate one or more of the reference surface points.
 10. The method ofclaim 1, wherein the feature on or near the viewed object is a missingcorner of the viewed object, and wherein the step of placing one or moremeasurement cursors on one or more measurement pixels of the image usinga pointing device comprises performing an area measurement by placing afirst measurement cursor on a first edge of the viewed object proximatethe missing corner at a first distance from the reference surfacepoints, placing a second measurement cursor on a second edge of theviewed object proximate the missing corner at a second distance from thereference surface points, and placing a third measurement cursor at athird distance from the reference surface points.
 11. The method ofclaim 10, further comprising the steps of: determining that the thirddistance is greater than the first distance and the second distance;determining an angle between (i) a first line extending between thefirst measurement cursor and the third measurement cursor and (ii) asecond line extending between the second measurement cursor and thethird measurement cursor using a central processor unit; and if theangle is within a predetermined range of angles, automaticallydetermining the area formed by the measurement cursors and the length ofthe first line and the second line.
 12. The method of claim 10, furthercomprising the steps of: determining the lengths of a first lineextending between the first measurement cursor and the third measurementcursor and a second line extending between the second measurement cursorand the third measurement cursor using a central processor unit; anddisplaying on the monitor the dimensions of the area formed by themeasurement cursors and the lengths of the first line and the secondline.
 13. The method of claim 10, further comprising the steps ofdisplaying on the monitor a first extension line extending from thethird measurement cursor through the first measurement cursor along thefirst edge of the viewed object and a second extension line extendingfrom the third measurement cursor through the second measurement cursoralong the second edge of the viewed object.
 14. The method of claim 1,further comprising the steps of: determining a distance between a pointon the surface of the viewed object and the reference surface using thecentral processor unit; comparing the distance to a predetermineddistance threshold using the central processor unit; and displaying anoverlay on a pixel in the two-dimensional image associated with thepoint on the surface of the viewed object if the distance is below thepredetermined distance threshold.
 15. The method of claim 14, whereinthe distance is the perpendicular distance between the point on thesurface of the viewed object and the reference surface.
 16. The methodof claim 1, further comprising the steps of: determining a distancebetween a point on the surface of the viewed object and the referencesurface using a central processor unit; comparing the distance to apredetermined distance threshold using the central processor unit; anddisplaying in a three-dimensional view of the plurality of points on thesurface of the viewed object an indication of the surface point having adistance below the predetermined distance threshold.
 17. The method ofclaim 1, further comprising the steps of: displaying on the monitor athree-dimensional view of the plurality of points on the surface of theviewed object; and displaying on the three-dimensional view a pluralityof field of view lines extending from a field of view origin to providea visual indication of the orientation of a tip of a probe of a videoinspection device with respect to the viewed object.
 18. The method ofclaim 1, further comprising the steps of: displaying on the monitor athree-dimensional view of the plurality of points on the surface of theviewed object and the reference surface; and displaying a guideline onthe three-dimensional view extending from one of the one or moreprojected reference surface points associated with the one or moremeasurement cursors on the reference surface to a point on the surfaceof the viewed object, wherein the guideline is perpendicular to thereference surface.
 19. The method of claim 1, wherein the referencesurface is a reference plane, further comprising the steps of:determining an edge view plane based on the three-dimensionalcoordinates associated with at least two of the measurement cursorsplaced on an edge of an object using the central processor unit;determining an angle between the reference plane and the edge view planeusing the central processor unit; and if the angle is outside of apredetermined range of angles, indicating a warning on the monitor.